Add Executor and JSON tester for Executor

Executor is an addon that acts as a shim between the XBMC JSON-RPC API and XBMC's built-in RunScript function. Using this addon, we no longer require the HTTP API and can move from Eden to Frodo.

JSON test is a basic web page that exercises Executor using the JSON-RPC API. The source directory should be placed in the webinterface.awxi directory (technically it should be possible to simply rename index.html and place it in the existing source directory) and the python files in the vaderScripts directory. It may be necessary to replace D: with C: in the index.html to make the page work on the VADER box.