[SPARK-1779] Throw an exception if memory fractions are not between 0 and 1

Author: wangfei <scnbwf@yeah.net>
Author: wangfei <wangfei1@huawei.com>

Closes #714 from scwf/memoryFraction and squashes the following commits:

6e385b9 [wangfei] Update SparkConf.scala
da6ee59 [wangfei] add configs
829a195 [wangfei] add indent
717c0ca [wangfei] updated to make more concise
fc45476 [wangfei] validate memoryfraction in sparkconf
2e79b3d [wangfei] && => ||
43621bd [wangfei] && => ||
cf38bcf [wangfei] throw IllegalArgumentException
14d18ac [wangfei] throw IllegalArgumentException
dff1f0f [wangfei] Update BlockManager.scala
764965f [wangfei] Update ExternalAppendOnlyMap.scala
a59d76b [wangfei] Throw exception when memoryFracton is out of range
7b899c2 [wangfei] 【SPARK-1779】

core/src/main/scala/org/apache/spark/SparkConf.scala

@@ -238,6 +238,20 @@ class SparkConf(loadDefaults: Boolean) extends Cloneable with Logging {
       }
     }
 
+    // Validate memory fractions
+    val memoryKeys = Seq(
+      "spark.storage.memoryFraction",
+      "spark.shuffle.memoryFraction", 
+      "spark.shuffle.safetyFraction",
+      "spark.storage.unrollFraction",
+      "spark.storage.safetyFraction")
+    for (key <- memoryKeys) {
+      val value = getDouble(key, 0.5)
+      if (value > 1 || value < 0) {
+        throw new IllegalArgumentException("$key should be between 0 and 1 (was '$value').")
+      }
+    }
+
     // Check for legacy configs
     sys.env.get("SPARK_JAVA_OPTS").foreach { value =>
       val warning =