added Filters to Media

I've added some filters to Media : 
Video : 
* Faststart
* PixelFormat : to manage -pix_fmt
* Preview : generate a preview with TimeCode (start, end)

Audio : 
* Mono : force mono 
* Volume : to in/decrease volume ( -vol )

Frame : 
* Quality : to manage quality of output ( -qscale )
* Single : to generate a single image
* Timeline  : to generate multiple thumbnails ( each seconds, each minutes, ... )

I've modified x264 format to use a preset or use your default command