Added Doxygen config file.

- Updated .gitignore to exclude tags file and doxy output.
- Minor makefile changes.

Signed-off-by: Chris Reed <flit@me.com>
Many new unit tests and some rvalue ref handling fixes.

- Fixed operator= and ctors that take rvalue refs so move semantics work
  as expected, by adding missing std::move() around params.
- Added reset() method to TokenIterator, mostly to help unit tests.
- Lots of test case additions.

Signed-off-by: Chris Reed <flit@me.com>