Priority Queue and Tracklist filter enhancement

[unknown0816]

I have developed two branches of mopidy. Each enhanced a specific feature that was missing from my point of view.

1. Being able to have a priority list in the tracklist, that will be used first when a new track is selected. There are two possibilities to set the priority. One uses an internal counter that will be decreased with each call. The other function must be provided with a value that will be set. Afterwards the queue will be resorted. This feature is inspired from the MPD feature prio.
   https://github.com/unknown0816/mopidy/tree/prio_support
2. The already existing function filter in the tracklist was online usable in case the exact string was provided. It was a full case sensitive search. I changed this to a case insensitive search that will also find substrings. Further I added an any field to the Track structure which has all necessary information included. So it is possible to use any and search for track name, artist and album at once.
   https://github.com/unknown0816/mopidy/tree/filter_extension

However, in case the branches do not work, the reason could be that I could set up the correct dev-environment and had to be a little hacky. So I couldn't actually test my github-branches. I tested it with an older version of mopidy, which was modified directly. Afterwards I copied the changes to the branches.

Should I create Pull-Request for these two branches?