Ruby bindings and bugfixes for LightMediaScanner

Thanks to Levi Bard we now have ruby-lightmediascanner, with even API docs!

On the bug fixes front, after Canola2 was released and it was tested with multitude of media I could fix lots of bugs with parsers, mainly on jpeg and id3lib.

Last but not least, thanks to Renato Chencarek we now have ogg support, and I also added png and audio-dummy to register known media files we still have no specific parsers (real, wma, ...)

It's already stable, when I have time I'll add a non-dual process version of process and check, so people with "correct" media files can use this and benefit from a much faster version (however this will rely on developers adding support to choose both implementations).