Support github repos with utf-8 dictionaries for dictionary download

[Predelnik]

Examples:
https://github.com/titoBouzout/Dictionaries
https://github.com/wooorm/dictionaries

Unfortunately currently they are not parsed correctly.

[Predelnik]

For https://github.com/titoBouzout/Dictionaries it's fairly easy, mostly list is empty because of "Show only recognized" option which is not that important now so I will probably just make it false by default

For https://github.com/wooorm/dictionaries all dictionaries filenames are index.aff/dic so it will require a bit more work and I will postpone it most likely.