[FEATURE] Add CollectionViewHelper

It's the first time I try to commit something on Github, so help me out if I'm doing something really wrong.

I didn't know to what category to add this VH to, so feel free to relocate it.
@NamelessCoder sorry for monstrous delay!
`RecordCollectionRepository` is not a real extbase repository, so I think what you are suggesting would not work, look-up the source for yourself.

The only way I can think of how to make it to work, is to manually loop over the uids, findByUid records and merge them together into one array. But is it something really needed? If yes, then I'll try to add that feature tomorrow.