Fix name collision of variable P and function P()

[mtmccrea]

There was a name collision of variable P and function P(), this was fixed previously, but it left out the correction in the if clause for the case of complex SHs. To generalize the correction, all of the functions that generate the P, U, V, and W terms are called getP, getU, etc. Because these are local functions it won't impact backward compatibility.

There's also a typo fix and minor change to the function that plots spherical functions, which adjusts the edge alpha so it's less distracting, esp. for very dense designs.

[mtmccrea]

After looking more closely (I had a diverging version history), this is a redundant change with Leo's previous fix of the same issue, but I still think the renaming of the functions is useful for clarity.