Add ability to remove tags & performers

[damontecres]

#49 & #51 adds the ability to add tags & performers

It might be useful to also be able to remove them (like undo). This might be doable with a long click, but it's a bit more complex to add a long click listener to a leanback fragment: https://stackoverflow.com/questions/30163902/how-to-implement-a-longclicklistener-on-browsefragment-android-leanback-library

Could instead add an Undo action if changes have been made, but this would require tracking the changes which is also not simple.

Originally posted by @damontecres in #3 (comment)