Lexer for expression PSI

Ported from the IntelliJ plugin
Tiny tidy up
AngularJs PSI language + (failing) parser tests
Parsing simple repeat expressions
Parsing repeat expressions

Tests still broken due to not parsing filters properly
Added expression to gold files to aid debugging
Rewritten parser to match angular.js source

JavaScriptTreeBuilder isn't flexible enough to override just the bits we
need, so re-implementing the parser based on the code in the angular.js
source. Some tests not working (stack overflows!) so commented out for
now.
Parsing properties and function calls
Break out of infinite loops

So more tests simple fail, rather than die
Filter tests passing
Green tests for parser!
Updated license notices in files
Inject AngularJS PSI into HTMl ng- attributes
Highlighting syntax errors!