Parse less and scss and collect all css rules.
Make `Quick Find Definition` work in scss and less files.
Parse nesteds rules in less and scss files.
Better handling of nested rules by skipping nested at-rules, line comments and block comments.
Also provide full selectors showing all the parent selectors in Quick Edit and Quick Find Definition.
Get the complete selector for nested group parents.
Don't show descendent selectors when searching on an ancestor selector.
Fix the group start line and group start char for nested levels.
Show parent selectors with ` / ` as separators.
Include comments in nested rules.
Fix the issue of last property with no ';' causing runaway nested rule.
Skip @include and @extend in scss.
Improve robustness in code that skip properties.
Clean up unneeded code in _getParentSelectors.
Add some comment JSDoc for mode param.
Handle nested levels correctly for @media rules.
Merge remote-tracking branch 'origin' into rlim/parse-less-and-scss

Conflicts:
	src/language/CSSUtils.js
Remove commented code.
Fix unit test failures by removing unneeded code that was added during experiment for parsing nested rules.
Fix the two remaining unit test failures.
Convert all regex.match() to regex.test() calls.
Fix the nested level issues in @media block.
Fix the rule start line issue caused by a comment at the end of the previous rule.
Add JSDoc and comment for the new functions.
Fix  one CSS Parsing unit test failure.
Fix the issue of picking up some portion of parameterized property values as nested selectors.
Fix the issue of not picking up some selectors like `> li > a {` due to CM parser state.
Implement a better solution to skip all the commas in parameterized properties or functions.
Parse @mixin rule lists like normal rule list by excluding them from at-rule parsing.
Clean up convoluted logic and properly decrement one level after processing an @media block.