Added the ability to ignore albums

As response to issues #1364 and #740.
My reason of adding this was the album http://musicbrainz.org/release-group/c057f7e1-e811-48fc-88b6-3d9d55c26009 . Since there is no chance this album will ever be available digitally, I don't want to include this in my collection.
I'm pretty OCD, so the 100/111 on the index has been bothering me.

I took the liberty to add a style and pick a random icon for the "Manage Albums" list.

I have to say, this hasn't been tested on a heavy database, so I don't know how much resources my added/changed queries will take..

Feedback is greatly appreciated :)