Remove DemoPlugins

Not built, not needed, so remove them. Even as examples they fail.
MovieSelection: Fix some whitespaxes
MovieSelection: Add option to hide known extensions

And remove some more white spaces
MovieSelection: Better description an simpler coding
UsageConfig: Latvian should be lav instead of lat

Thanks Artis

See: http://openpli.org/forums/topic/21339-automatic-language-subtitle-settings-improvements/page__st__40
configure.ac: simplify vu+ boxtype detection
MovieList: Add pictures to the known extensions

And do it slightly different - thanks DeBeek
MovieSelection: Remove delayTimer use callLater instead

As callLater does in fact the same
MovieSelection: Remove extension code/data duplication and speed it up

Put the "known extension types" lists in one spot for easy maintenance.

Doing "a in (very,big,tuple)" will sequentially scan all elements of
the tuple. This is much slower than a set or frozenset which uses a
hash lookup.
Merge remote-tracking branch 'pli/master'

Conflicts:
	configure.ac
	lib/python/Screens/MovieSelection.py