THEME-COLIBRI 6: Upgrade from lessc 1.3.0 to lessc 1.4.2
    - Needed in order to use the less 'extend' function
    - grunt-recess is using 1.3.0 that's why I replaced it with grunt-contrib-less
[misc] Building Colibri Theme with grunt-contrib-less
THEME-COLIBRI 6: Upgrade from lessc 1.3.0 to lessc 1.4.2
THEME-COLIBRI 5: XWiki.less - mapping clearfloats
- fixed the duplication code after mixing call by using 1.4.2 extend function