Provide scripting feature for data access manager

In the resource orientated programming style, one can use the URI as a way to script the application. For example, scripting feature in NetKernel (http://docs.1060.org/docs/3.3.0/book/solutiondeveloperguide/doc_guide_Scripting.html).

In GumTree, we will provide script evaluation via the data access manager, for example:

// URI -> script://jython/1+1
dam.get(URI.create("script://jython/1+1"), Integer.class)

Above code will evaluate the script and return the result as a resource to the client.

Limitation:
There will be no type conversion for this script data provider, as there are many possibility of the result type.