[Design] - Prototype of ResourceModel

/cc @yishaigalatzer @harshgMSFT 

Not included here:
- Model Metadata integration
- Sample generation interface
- Filter interface for customizing formatters

Where possible I made decisions that are similar to webapi api explorer. See comments in the code for context on specific decision points and open questions.
This is really interesting. This method for getting filters is totally broken, because it violates the contract of IFilterFactory. To do this correctly we need to get the FilterProvider and call that, but that requires an action context, which requires a request.

Need to think more about this.