Make SFX items editable

[jonko0493]

#293 introduced SFX items but they're still not editable.

We should be able to replace a given SFX with a wave that gets pulled into a wave archive, and then create a new instrument bank that uses that wave, and then finally specify which sequence archive and group(s) to put the SFX in. We should encourage users to not put their SFX in ONMEM to avoid OOM exceptions, but instead to put it in the groups that get loaded in the scenes they need.

Additionally, we should consider allowing the user to import files from NitroStudio containing MIDI information for the file.