MiasMod: Add initial support for managing main.rs5 mods

This displays the installed main.rs5 mods, can install new ones from
rs5mod files and can revert main.rs5 back to it's original state.

It displays the mod order, but currently has no way to set it.

Currently there is no way to remove an individual mod.
MiasMod: Add ability to remove rs5 mods & set mod order

These actions are done via a right click context menu. Potentially the
mod order could be handled a bit better, but this is probably good
enough for now.