Add includeJS keyword which allows interpreter to run remaining code in a continuation.

Caveats: includeJS usage inside of functions will break things. Use at top level only.
         had to delete the code that modified lexer at runtime for this change.
fix typo
Test for includeJS.
Cleanup js/core/eden.js
Consistency between plugins, plugins now only use "root" directly instead of "context.context".
Clean up initialise.js
Querystring option for loading JSE file from URL on load.
Replace use of eval/translate with execute.

Benefits of doing so:
- decouple various things from how eden is evaluated. For example, doing
  `eval(translateToJavaScript(blah)` needs `root` and `rt` in scope to work
  correctly.
- get consistent handling of errors during evaluation of eden code. Previously
  error handling logic was sometimes written at each call site, using `Eden.execute`
  means the error handling is taken care of for you.
Forgot config for jse proxy.
Whoops, use relative url instead of absolute url for config.json.
Merge branch 'master' of https://github.com/emgroup/js-eden