Add ability to find sticker key with a specific value/range

[khaytsus]

I'd like to be able to ask mpc to return songs with a sticker key with a specific value, my specific need is to find a sticker key named "rating" that is greater than or equal to a value, ie something like this:

mpc sticker "" find "rating>=6"

Finding all files with a given key, ie: mpc sticker "" find rating works fine, but can mpc return only specific results? It already has many other options in find/search to get specific song attributes, being able to filter the sticker keys would be terrific. Thank you!

This has been implemented in MPD itself via this issue: MusicPlayerDaemon/MPD#759