[FEATURE] Add ability to reorder queue

[xxxserxxx]

Users should be able to re-order the queue, moving individual songs up or down. While we're at it, a "shuffle" operation would be nice.

All of the good bindings are already taken; +/- control the volume; arrow keys navigate. I'm inclined to use vim bindings: k/j for up/down. s is free, so how about S for shuffle? Capital-S, just to make it a little harder to accidentally shuffle.

This is probably a good beginner ticket, which also makes it likely I'll just add it and submit a PR. I'd like feedback on the key bindings, though: any better ideas?

[xxxserxxx]

This is implemented with PR #37; the automagic cross-reverence wasn't made because my fork was originally made from wildeyedskies, and I haven't yet deleted and re-forked it.