Add fileExt, importOption options, use global less

* fileExt option to specify default file extension
* importOption option to set the way of resource importing
* ability to use preloaded global less
* ability to use global less configuration
* adaptation to curl configuration
Include provided paths config parameter
Update README.md
Merge remote-tracking branch 'remotes/SamHowie/master'
Merge remote-tracking branch 'remotes/gamtiq/master'
Merge remote-tracking branch 'remotes/westmark/master'