Remove throws clause from main methods, and exit on Exceptions

This causes the RadarGun processes to exit as soon as an exception is
thrown. I have had issues with the processes not exiting when run in
Jenkins.
Fixes for ISPN-2836

This commit adds support for the new timeout API added in Infinispan
5.3, and adds error handling for exceptions thrown from
MapReduceCapable.executeMapReduceTask()
Updates to the random data generator

Remove usage of "this"
Modify the random word generator to prefer double byte characters, so
that the length of the byte array is closer to the size of the String
object
Add the ability to restrict the set of words to a pre-generated list and
provide a way to share the list among the nodes in the cluster
Fix issues with memory overhead of writing String objects to cache

String objects have an overhead that is twice the size of the byte array
used to create the String plus the normal overhead for writing an entry
to the cache.
Fix review comments

- Use strings to generate random words, instead of byte arrays
- Simplify code in initOnMaster that generates the shared words array
- Rename variables and methods
- Remove spurious call to String.intern()
More cleanup from review comments

Remove initOnMaster altogether. Use the same Random object seed on all
nodes in the cluster to generate the same list of words. Change default
seed value, so that all nodes share the same seed value.

Update comments
Rename length variables that refer to byte lengths, since strings you
character arrays
Merge branch 't_randomdata' of https://github.com/alanfx/radargun into
t_randomdata

Conflicts:
	framework/src/main/java/org/radargun/stages/RandomDataStage.java