libgupnp-dlna: Use encoding-profile from plugins-base

libgupnp-dlna: Use encoding-profile from plugins-base

- Give up on the local copy of gstprofile (from gst-convenience) and use
  the encoding-profile api from gst-plugins-base.

- Stop using GstEncodingProfile for in memory representation of the on
  disk XML profiles but rather create GstEncodingProfile on the fly.

- We now use a single GstCaps variable each for audio/video and container
  instead of a GList and merge them as they are processed from the XML file.