[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.
> 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

I agree, that does look like the only way to do it. I think we need to dial this back and let the ViewHelper only load a single Collection at a time, by UID (sort of like what the Resource ViewHelpers do). This would allow developers to use it for loading any number of Collections and would prevent any confusion/obscurity issues regarding which type of value is returned (instance or Array) when only a single Collection is loaded vs. when multiple are loaded.

It also makes it a lot simpler to create ;)