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

Double conversion is not good for performance. Do this in the execute function and pass the exact reported DOM point to the verification function. E.g.,: 
``
var firstParagraph = odtDocument.convert...();

verifyFirstStepInParagraph(odtDocument, firstParagraph);
```