video-encode: Use VP8 as alias for VPX.
video-encode: Map all streams.
video-encode: Remove max bitrate for VPX.
video-encode: Adjust VPX quality.
video-encode: Add theora vcodec.
video-encode: Allow to specify the output file.
video-encode: Avoid hidden directory for encoded

We used an hidden directory for encoded files. However if someone does
not pay attention, he may not know about this directory as it is not
clearly visible. We now use the 'encoded' directory to store original files.