navpy.py: Added docstrings for angle2dcm and dcm2angle

navTest.py:
1. Added ecef2lla test
2. Added lla2ecef test
3. Added dcm2angle test
4. Adopted the new function name for wrapping angles to [-PI,PI]. New name is
wrapToPi to align it with MATLAB. navTest.py reflects this new name.
5. Migrated angle2dcm test.