added basic suport for embedding (html5) videos
Add several alternative formats to video for better browser compatibility

All .webm, .ogv and .mp4 files with the same filename are automatically
chosen as alternative sources when only one of them is mentioned in the
media syntax.
added poster attribute to video if jpg or png with same file name exists
improved code for videos (restrict to 3 mimetypes, removed codec info from type attribute)
added support for html5 audio

Similar to videos, all .ogg, .mp3 and .wav files with the same filename are automatically chosen as alternative sources when only one of them is mentioned in the media syntax.
fixed typo
refactored audio/video code, removed wrong link around audio
added spacing below video and audio elements

Note: The spacing will now show as too much as long as the paragraph bug
is not fixed
Merge remote-tracking branch 'origin/master' into video-audio
Merge remote-tracking branch 'origin/master' into video-audio

Conflicts:
	inc/parser/xhtml.php
Merge remote-tracking branch 'origin/master' into video-audio
fixed html errors in video and audio rendering
Merge remote-tracking branch 'origin/master' into video-audio
Merge pull request #265 from splitbrain/video-audio

Added video and audio support