extend plot_main_apertures to also plot HST or Roman apertures

[mperrin]

This PR updates the plot_main_apertures function to add a new parameter mission, which allows choosing to plot the JWST, HST, or Roman SIAF apertures.

pysiaf.siaf.plot_main_apertures(mission='JWST')
pysiaf.siaf.plot_main_apertures(mission='HST', fill=False)
pysiaf.siaf.plot_main_apertures(mission='Roman')

(Minor note, I don't know why for HST it defaults to filling the apertures, but for JWST and Roman it does not. In fact the plot function seems incapable of filling those apertures, regardless of whether plot=True or plot=False is set. Also, COS is not included for HST because the plot function can't handle circular apertures currently. Fixing either of those issues is out of scope for this PR however).

[tonysohn]

Tested successfully. I approve this change, and also agree that we should (1) get rid of filling HST apertures by default and (2) add ability to plot circular COS apertures.