2D Editor Example Application

**Motivation:** Experience the framework from the perspective of an application developer who wants to build an app on the VWF by creating a 2D, multi-user document editor similar to Google Docs. 

**Features:**
- Live document editing by multiple users
- Save and load documents
- Show documents that are actively being edited *(not yet implemented)*
- Show name of users that are currently editing *(not yet implemented)*
- Show the cursor location of users while editing *(not yet implemented)*

This doesn't need to be merged in just yet, just wanted to get the code up in a place where other people could take a look at it.

[Redmine #2630](http://redmine.virtualworldframework.com/issues/2630)

(Continuation of #14, but tracking integration.)