- Converted unit tests to use a UnitTest object, with more methods and
and exit summary.
- Removed "fail" tests in tdb.t.cpp, because it artificially reduces
the number of passing tests - the comments in the code suffice.
- Added unit tests for Date enhancements
- Added unit tests for duration recognition
- Task parsing now supports due: using relative dates
- Task parsing now supports recur: and until: attributes
- Task parsing now support private attributes base: and range:
