Add support for generic adaptor

This adds support for a generic adaptor that can be used with any graph JS visualisation library.  The `d3adaptor` is a derivative of `cola.adaptor`, and isolates all D3-related code.

I've also updated project references to the new `adaptor.js` file which replaces `d3adaptor.js`.  

I can't run the tests, as they seem to require Visual Studio to compile the TS rather than Grunt.  However, the Grunt build tasks still work and I've confirmed that the new `cola.d3adaptor` works with the `ariel.html` example after building.