[SPARK-4329][WebUI] HistoryPage pagenation

Current HistoryPage have links only to previous page or next page.
I suggest to add index to access history pages easily.

I implemented like following pics.

If there are many pages, current page +/- N pages, head page and last page are indexed.

![2014-11-10 16 13 25](https://cloud.githubusercontent.com/assets/4736016/4986246/9c7bbac4-6937-11e4-8695-8634d039d5b6.png)
![2014-11-10 16 03 21](https://cloud.githubusercontent.com/assets/4736016/4986210/3951bb74-6937-11e4-8b4e-9f90d266d736.png)
![2014-11-10 16 03 39](https://cloud.githubusercontent.com/assets/4736016/4986211/3b196ad8-6937-11e4-9f81-74bc0a6dad5b.png)
![2014-11-10 16 03 49](https://cloud.githubusercontent.com/assets/4736016/4986213/40686138-6937-11e4-86c0-41100f0404f6.png)
![2014-11-10 16 04 04](https://cloud.githubusercontent.com/assets/4736016/4986215/4326c9b4-6937-11e4-87ac-0f30c86ec6e3.png)

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #3194 from sarutak/history-page-indexing and squashes the following commits:

15d3d2d [Kousuke Saruta] Simplified code
c93932e [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into history-page-indexing
1c2f605 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into history-page-indexing
76b05e3 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into history-page-indexing
b2240f8 [Kousuke Saruta] Fixed style
ec7922e [Kousuke Saruta] Simplified code
755a004 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into history-page-indexing
cfa242b [Kousuke Saruta] Added index to HistoryPage

core/src/main/scala/org/apache/spark/deploy/history/HistoryPage.scala

@@ -26,6 +26,7 @@ import org.apache.spark.ui.{WebUIPage, UIUtils}
 private[spark] class HistoryPage(parent: HistoryServer) extends WebUIPage("") {
 
   private val pageSize = 20
+  private val plusOrMinus = 2
 
   def render(request: HttpServletRequest): Seq[Node] = {
     val requestedPage = Option(request.getParameter("page")).getOrElse("1").toInt
@@ -39,6 +40,9 @@ private[spark] class HistoryPage(parent: HistoryServer) extends WebUIPage("") {
     val last = Math.min(actualFirst + pageSize, allApps.size) - 1
     val pageCount = allApps.size / pageSize + (if (allApps.size % pageSize > 0) 1 else 0)
 
+    val secondPageFromLeft = 2
+    val secondPageFromRight = pageCount - 1
+
     val appTable = UIUtils.listingTable(appHeader, appRow, apps)
     val providerConfig = parent.getProviderConfig()
     val content =
@@ -48,13 +52,38 @@ private[spark] class HistoryPage(parent: HistoryServer) extends WebUIPage("") {
             {providerConfig.map { case (k, v) => <li><strong>{k}:</strong> {v}</li> }}
           </ul>
           {
+            // This displays the indices of pages that are within `plusOrMinus` pages of
+            // the current page. Regardless of where the current page is, this also links
+            // to the first and last page. If the current page +/- `plusOrMinus` is greater
+            // than the 2nd page from the first page or less than the 2nd page from the last
+            // page, `...` will be displayed.
             if (allApps.size > 0) {
+              val leftSideIndices =
+                rangeIndices(actualPage - plusOrMinus until actualPage, 1 < _)
+              val rightSideIndices =
+                rangeIndices(actualPage + 1 to actualPage + plusOrMinus, _ < pageCount)
+
               <h4>
                 Showing {actualFirst + 1}-{last + 1} of {allApps.size}
-                <span style="float: right">
-                  {if (actualPage > 1) <a href={"/?page=" + (actualPage - 1)}>&lt;</a>}
-                  {if (actualPage < pageCount) <a href={"/?page=" + (actualPage + 1)}>&gt;</a>}
-                </span>
+                  <span style="float: right">
+                    {
+                      if (actualPage > 1) {
+                        <a href={"/?page=" + (actualPage - 1)}>&lt; </a>
+                        <a href={"/?page=1"}>1</a>
+                      }
+                    }
+                    {if (actualPage - plusOrMinus > secondPageFromLeft) " ... "}
+                    {leftSideIndices}
+                    {actualPage}
+                    {rightSideIndices}
+                    {if (actualPage + plusOrMinus < secondPageFromRight) " ... "}
+                    {
+                      if (actualPage < pageCount) {
+                        <a href={"/?page=" + pageCount}>{pageCount}</a>
+                        <a href={"/?page=" + (actualPage + 1)}> &gt;</a>
+                      }
+                    }
+                  </span>
               </h4> ++
               appTable
             } else {
@@ -81,6 +110,10 @@ private[spark] class HistoryPage(parent: HistoryServer) extends WebUIPage("") {
     "Spark User",
     "Last Updated")
 
+  private def rangeIndices(range: Seq[Int], condition: Int => Boolean): Seq[Node] = {
+    range.filter(condition).map(nextPage => <a href={"/?page=" + nextPage}> {nextPage} </a>)
+  }
+
   private def appRow(info: ApplicationHistoryInfo): Seq[Node] = {
     val uiAddress = HistoryServer.UI_PATH_PREFIX + s"/${info.id}"
     val startTime = UIUtils.formatDate(info.startTime)