[3D] add support for stereomode detection of other codecs than MKV

This PR is abstracting the stereoscopic detection to a separate function and is adding stereoscopic detection for wmv/asf files (see http://www.3dtv.at). Not sure if this is the correct way to go, so @elupus please have a look.
I prefer multiple separate maps yes (the function can be generic and take a reference to the map as parameter). There is no guarantee different codecs won't have conflicting options, and i want it to be clear this is from WMA/ASF