Integration of core info files in RGUI.

I've started to integrate core_info into RGUI. The main idea here is to add support for autodetection of libretro cores.
I've also added support for autodetection even through the ZIP boundary, so should be very user friendly to load games.

Ofc, this feature requires core info files to be present. I've made some slight refactoring to core_info overall to match the coding style better.

It's not quite finished yet though, but I'll like some comments on stuff.