New Timer utility for measuring CPU and wall times

Includes thread-aware timer registry for time
taking across multiple threads.
Modified tests to be more robust (esp. on OpenJDK6)

Unfortunately, time measurements are somewhat random
and cannot be predicted very well. The tests could still
fail randomly if some very unusual runtimes occur.
Completed JavaDoc comments
Fixing issue #27.
Merge pull request #7 from Wikidata/wdtk-util-timer

New Timer utility for measuring CPU and wall times
Extended documentation of constructor parameters
Merge pull request #28 from Wikidata/issue-#27

Fixing issue #27.
Support very large (or very small) years

This fixes issue #30.
Merge pull request #31 from Wikidata/issue-#30

Support very large (or very small) years
Merge remote-tracking branch 'origin/master' into jsonToDataModel
Switching to long for years.