Re-work to allow dynamic compilation of framework

** Note: this requires the framework cloned to adapt_framework in the root
of the adapt_authoring project **

Publish and Preview now read from the tenant specific build folder.
Dynamically building the framework

When Publish or Preview is invoked, if a built framework does not already
exist the Grunt task is executed to build it.  (Currently the theme is
defaulted to 'adapt-contrib-vanilla').