Add sort method for lists

[MartijnKaijser]

Add sort methods to sort by artist/album/rating or whatever http://mirrors.xbmc.org/docs/python-docs/13.0-gotham/xbmcplugin.html#-addSortMethod

Need to check source code if all are actually on the list

[Dariusz Biskup]

Yep. This is in the plan.

[Petri Ahonen]

Only needs couple lines of code in UiHelper.py, I have patch for this and it works.

[Dariusz Biskup]

make playlist sort work, fix issue #27

→ <<cset 17ef6c4a4d6d>>