Set Python DeprecationWarnings to default. Refs #6639

In 2.7 they are ignored by default, which is not that useful.
Fix doxygen errors in Python Axis.cpp. Refs #6639
Add deprecated functions to new API to aid in transition. Refs #6639
Update Axis to remove createSpectraAxis method. Refs #6639
Merge remote branch 'origin/feature/6639_deprecated_python_cmds'
Change the default values of StartTime/StopTime.  Refs #6694.
Merge branch 'feature/6694_genfilter' into develop