adding weakidentitymap with tests.
adding PurgeableThreadLocal with tests and default purge strategy.
cleaning up xml comments and ensuring default strategy is set.
adding resharper & ghostdoc settings. refactoring code for consistency.
adding ByteBlockPool and Counter with tests
adding ByteBlockPool and Counter with tests
adding BytesRefArray.cs, need to swap out ByteRef for BytesRefBuilder after BytesRefBuilder is ported.