Playlist management and shift keys

The delete and backspace keys can now be bound and Shift can now be used as a modifier for alpha keybindings and arrow keys. For example:

J = move_down
j = select_down
K = move_up
k = select_up

up   = volume_up
down = volume_down

Up   = last_track
Down = next_track

The following commands have been added to help with playlist management	Command	Action
`move_up`	Moves the currently selected song up in the playlist
`move_down`	Moves the currently selected song up in the playlist
`shuffle`	Shuffles the playlist
`repeat`	Toggles playlist repeat on and off
`delete`	Removes the selected song from the playlist

GuardKenzie / miniplayer