Generic 2D client-side interface

[perrygeo]

We have a number of examples of purpose-built 2D client interfaces to Madrona. For the 5.0 release, it would be great to have a generic interface (similar to our current 3D interface) that can adapt to any madrona instance's API via the workspace document.

There are a number of considerations to the design:

• Tree-view and editing could be made more "google docs"-like
• form and show templates - client-side knockout or server-side django templates?
• Base layer management ala Marco
• ...

Lots of planning to do and design decisions to be made but at least the groundwork is laid by the first generation of 2D madrona projects.

[perrygeo]

We should consider an Angular JS and OpenLayers 3 implementation (based on my vague gut feeling about the future direction of advanced spatial web apps)