Clearer handling of magmom flag

[Andrew-S-Rosen]

Summary

Clearer Handling of Magnetic Moments

I have made a few additional clarifications to pymatgen.io.vasp.sets, primarily with regards to the handling of magnetic moments as a follow-up to #2301:

1. Clearer docstrings. This is rather self-explanatory.
2. Only print the warning about low magnetic moments on Co if the value is <= 1. If someone were to modify the default config to have high-spin Co, there is no longer a need for this warning. I had done this, and I found it somewhat bothersome.
3. If the user provides an integer for the magnetic moment, e.g. site["magmom"] = 1, then convert this to a float when get_valid_magmom_struct() is run. Previously, Pymatgen would crash when creating an Incar() object if the structure had an integer magnetic moment due to the lines below.

   pymatgen/pymatgen/io/vasp/sets.py

   Lines 3102 to 3106 in dd37370

   	elif isinstance(isite.properties["magmom"], float):
   	if mode == "v":
   	raise TypeError("Magmom type conflict")
   	mode = "s"
   	elif len(isite.properties["magmom"]) == 3:

Slight Adjustment to Handling of LASPH Warning

4. Extremely minor, but as a follow-up to Add warning if LASPH != True for meta-GGA/hybrid/vdW/+U #2297, I now check the Incar() object (rather than the settings variable) to see if LASPH is present. This is more robust.

[coveralls]

Coverage decreased (-0.6%) to 83.13% when pulling e6ba47b on arosen93:rosen-clarifications into dd37370 on materialsproject:master.

[Andrew-S-Rosen]

This one is good to go. It's just that broken Mac Windows test holding it up.

[mkhorton]

Thanks @arosen93 !