Fixing bug #5607

Changed the method from extends to merge which merges the two arrays as
desired - With Freyert
Fixed Issue #4012 Added Help menubar link to Github Flavored Markdown doc
Better lessc detection/handling.

* lessc@1.5.0 now invalid
* more help if lessc not found
Merge pull request #5633 from ahmadia/improve_no_lessc_error

Provide more help if lessc is not found.
Merge pull request #5613 from nilenoether/fix-5607

Fixing bug #5607 - Some shortcut missing from help reference.
Merge pull request #5630 from onceuponatimeforever/4012

Fixed Issue #4012 Added Help menubar link to Github markdown doc