[MiNT] updated XaAES wiki docs - Theming and Extended Textures

[Paul Wratt <paul.wratt@gmail.com>]

http://wiki.sparemint.org/index.php/XaAES#Theming_and_Extended_Textures

I spent a while on it, if anyone is interested. please verify (?)
facts, unknown to me atm

also verify concepts (texture file affects ..) and any instructions
for clarity and accuracy

and what are the options of some related files being made available on
Unofficial XaAES for download

let me know what peeps think

Paul
BTW thanks for all the work people have been putting to things, keep it up