build release with debug info
added stopwatch timer

A simple class that will track time from the point it is created and
allows you to capture snapshots of the elapsed time. The timer can be
reset at any time and can be reported with various levels of
granularity:

* seconds
* microseconds
* milliseconds
* nanoseconds
allow caller to get handle to threads
update changelog for 0.2.0 release
Fix tyename error
upgrade doxygen file format
Add Least Recently Used (LRU) cache