Loose parser: fixes and ES6

Done:
* Simplified some tests.
* Made driver to run already existing tests for both loose and normal parser.
* Fixed inconsistencies in loose parser for found errors (in regexes, arrays etc.).
* Added support for ES6 for loose parser with basic tolerance (might need extension in future for more cases).

Not done:
* There are still few ES5 tests that are failing and not sure what is the best way to fix.
* Template literals and tagged template literals from ES6 (not sure what is the best way to share / inject special tokenizer case for them).