I've added new utility methods to do the conversion from times specified as e.g. 120s, 240ms, 360us to convert to a consistent internal representation. I've updated usage of these constants throughout the code to be consistent.

I believe I've captured all usages of time-based properties throughout the code. I've also updated variable names in a number of places to reflect their units for clarity and updated documentation where appropriate.

Author: Ilya Ganelin <ilya.ganelin@capitalone.com>
Author: Ilya Ganelin <ilganeli@gmail.com>

Closes #5236 from ilganeli/SPARK-5931 and squashes the following commits:

4526c81 [Ilya Ganelin] Update configuration.md
de3bff9 [Ilya Ganelin] Fixing style errors
f5fafcd [Ilya Ganelin] Doc updates
951ca2d [Ilya Ganelin] Made the most recent round of changes
bc04e05 [Ilya Ganelin] Minor fixes and doc updates
25d3f52 [Ilya Ganelin] Minor nit fixes
642a06d [Ilya Ganelin] Fixed logic for invalid suffixes and addid matching test
8927e66 [Ilya Ganelin] Fixed handling of -1
69fedcc [Ilya Ganelin] Added test for zero
dc7bd08 [Ilya Ganelin] Fixed error in exception handling
7d19cdd [Ilya Ganelin] Added fix for possible NPE
6f651a8 [Ilya Ganelin] Now using regexes to simplify code in parseTimeString. Introduces getTimeAsSec and getTimeAsMs methods in SparkConf. Updated documentation
cbd2ca6 [Ilya Ganelin] Formatting error
1a1122c [Ilya Ganelin] Formatting fixes and added m for use as minute formatter
4e48679 [Ilya Ganelin] Fixed priority order and mixed up conversions in a couple spots
d4efd26 [Ilya Ganelin] Added time conversion for yarn.scheduler.heartbeat.interval-ms
cbf41db [Ilya Ganelin] Got rid of thrown exceptions
1465390 [Ilya Ganelin] Nit
28187bf [Ilya Ganelin] Convert straight to seconds
ff40bfe [Ilya Ganelin] Updated tests to fix small bugs
19c31af [Ilya Ganelin] Added cleaner computation of time conversions in tests
6387772 [Ilya Ganelin] Updated suffix handling to handle overlap of units more gracefully
5193d5f [Ilya Ganelin] Resolved merge conflicts
76cfa27 [Ilya Ganelin] [SPARK-5931] Minor nit fixes'
bf779b0 [Ilya Ganelin] Special handling of overlapping usffixes for java
dd0a680 [Ilya Ganelin] Updated scala code to call into java
b2fc965 [Ilya Ganelin] replaced get or default since it's not present in this version of java
39164f9 [Ilya Ganelin] [SPARK-5931] Updated Java conversion to be similar to scala conversion. Updated conversions to clean up code a little using TimeUnit.convert. Added Unit tests
3b126e1 [Ilya Ganelin] Fixed conversion to US from seconds
1858197 [Ilya Ganelin] Fixed bug where all time was being converted to us instead of the appropriate units
bac9edf [Ilya Ganelin] More whitespace
8613631 [Ilya Ganelin] Whitespace
1c0c07c [Ilya Ganelin] Updated Java code to add day, minutes, and hours
647b5ac [Ilya Ganelin] Udpated time conversion to use map iterator instead of if fall through
70ac213 [Ilya Ganelin] Fixed remaining usages to be consistent. Updated Java-side time conversion
68f4e93 [Ilya Ganelin] Updated more files to clean up usage of default time strings
3a12dd8 [Ilya Ganelin] Updated host revceiver
5232a36 [Ilya Ganelin] [SPARK-5931] Changed default behavior of time string conversion.
499bdf0 [Ilya Ganelin] Merge branch 'SPARK-5931' of github.com:ilganeli/spark into SPARK-5931
9e2547c [Ilya Ganelin] Reverting doc changes
8f741e1 [Ilya Ganelin] Update JavaUtils.java
34f87c2 [Ilya Ganelin] Update Utils.scala
9a29d8d [Ilya Ganelin] Fixed misuse of time in streaming context test
42477aa [Ilya Ganelin] Updated configuration doc with note on specifying time properties
cde9bff [Ilya Ganelin] Updated spark.streaming.blockInterval
c6a0095 [Ilya Ganelin] Updated spark.core.connection.auth.wait.timeout
5181597 [Ilya Ganelin] Updated spark.dynamicAllocation.schedulerBacklogTimeout
2fcc91c [Ilya Ganelin] Updated spark.dynamicAllocation.executorIdleTimeout
6d1518e [Ilya Ganelin] Upated spark.speculation.interval
3f1cfc8 [Ilya Ganelin] Updated spark.scheduler.revive.interval
3352d34 [Ilya Ganelin] Updated spark.scheduler.maxRegisteredResourcesWaitingTime
272c215 [Ilya Ganelin] Updated spark.locality.wait
7320c87 [Ilya Ganelin] updated spark.akka.heartbeat.interval
064ebd6 [Ilya Ganelin] Updated usage of spark.cleaner.ttl
21ef3dd [Ilya Ganelin] updated spark.shuffle.sasl.timeout
c9f5cad [Ilya Ganelin] Updated spark.shuffle.io.retryWait
4933fda [Ilya Ganelin] Updated usage of spark.storage.blockManagerSlaveTimeout
7db6d2a [Ilya Ganelin] Updated usage of spark.akka.timeout
404f8c3 [Ilya Ganelin] Updated usage of spark.core.connection.ack.wait.timeout
59bf9e1 [Ilya Ganelin] [SPARK-5931] Updated Utils and JavaUtils classes to add helper methods to handle time strings. Updated time strings in a few places to properly parse time