Create numbered and bulleted lists

This PR aims to add the creation of lists in a document. This only aims to support numbered and bulleted lists and not image bullet lists for now.

# TODO
* [x] Editor UI buttons
* [x] Detect list style at selection
* [x] Ops for list insertion/removal
* [x] OT support
* [x] Convert selected text to a list or selected list back to text
* [x] Add feature flags and session constraints
* [x] Default styles for numbered and bulleted lists

@kossebau @adityab just want to call attention to this side-effect of the current ``REVIEW_MODE`` implementation. This brand new controller has to grow knowledge for a concept completely unrelated to lists in order to support review mode. When the next mode is invented, **every** controller in WebODF will need to gain knowledge of it.