began seperating parser and ast, error codes for bootstraper

[mvcisback]

Most of the diff shows me seperating js_ast and parser. I wanted to start doing this since its easier to decouple the parsers that way (before adding acorn support)

Also added in missing functions from application validator that were somehow not in the code base.

[erikrose]

Looks good. I'll make you a contrib so you can merge it in yourself. Remember to say something informative in the commit message and ref the pull req #. You can look to https://github.com/mozilla/dxr/commit/ef708edf96b6cd27ac4b4d2d768458be864e6445 as an example.