Add ability to "play next"

[Rawrior]

We want to be able to add a song to the top of the queue.

Not exactly sure how this could be done, since the parsing of the command for the enumeration would have to be expanded kind of a lot.

Otherwise the creation of the enumerator could be changed, so that you could write next [player] [search term]

[SEbbaDK]

We could add it via an exclamation point, so 5! would add 5 to play next.

This also works with the new multiadd feature.