Fix #3094: Refactor JSLint into an extension

This request fixes the issue #3094 by refactoring JSLint into an extension. I also did several changes in JSLintUtils, now being the main file in the extension as a result of the refactor, to use a template for the table and use Language to identify JavaScript files instead of the extension. I was also able to move the JSLint submodule to the extension.

Note: Not sure why it didn't renamed JSLintUtils to main and show the differences.