Favorites

Added features:

- Can populate rom menus directly. Implemented for SNES and Genesis, but easily extendible by adding a context entry (see EMU_CONTEXT), and a menu entry.

- Favorites menu - can add favorite roms by clicking 'z'/'x' (choice made because of my personal key mappings. Feel free to change). Similarly, pressing 'z'/'x' while in favorites will delete a rom.

Note: I used the previous menu version (without the N64) edition.