change main functions for PhenomD and PhenomX

[tedwards2412]

• Function names should be "gen_Phenom..._hphc"
• Function signature should be gen_Phenom..._hphc(f, theta, **kwarg)

The default mode of each waveform should fail if you do not pass in an f_ref argument

[tedwards2412]

#14 makes the initial change i.e. changes PhenomD and PhenomXAS waveform generators to use the hphc function naming rather than polar