Allow loading ROMs from ZIP files

[Sik]

A lot of ROMs (pretty much anything from a ROM set, for starters) come in ZIP files and even if space isn't a concern, having to explicitly extract them just to use them in BlastEm is an annoyance, especially when it needs to be done for every game.

Probably the easiest way would be to use libzip:

• Use zip_open to open the archive
• Use zip_get_num_entries and zip_stat_index to loop through all files in the archive until finding a filename that looks like a possible ROM
• Use zip_fopen, zip_fread, zip_fclose to extract the ROM from the archive
• Then finally zip_close the archive

If no ROM has been found within the archive, just throw an error message.

[mikepavone]

This was implemented in 0.6.2