Merge pull request #1523 from am11/master

srv-rtlcss: Prevent from throwing
Browser Link: Fixed NullReferenceException
JSON: Check for new schemas every 3 days
Remove redundant autoprefixer call
Stringify prev source maps
Merge pull request #1525 from MohammadYounes/f1

Possible fix for error described in PR#1523
BrowserLink: Removed CSS sync

This will be in the box in VS2013 Update 4
Use maps toJSON behavior
Merge pull request #1526 from MohammadYounes/f2

postcss maps are using toJSON behavior
Make rtlcss autoprefixer params optional
Keep map sources
Update source/target files paths
Merge pull request #1531 from MohammadYounes/f4

Update LESS/SCSS source-maps generation flow