Folder redirects for face previews

[focustense]

The documentation currently has some guidance on renaming mugshot folders if they don't quite match up, but this is limited and a little user-unfriendly. A better way to handle this is name-based redirects.

In other words, let me set up a mapping from "Bijin NPCs" to "Bijin NPCs SE" to tell EasyNPC that they're the same mod, and to use mugshots of one for the other. This isn't just for renamed mods, it's also going to be very useful if a mod author releases an AIO version of previous standalone mods, as was the case with Pride of Skyrim AIO. If someone has a few of the older PoS overhauls but doesn't want to download the whole AIO, they should be able to use the mugshots from the AIO. The app will still know that the plugin isn't installed, so this shouldn't trick anyone into making invalid selections.

This could go on the Settings page, as a simple grid of source->destination text or combo boxes.