[TASK] Remove css files and add scss files and gruntfile instead

Releases: 2.0.0
Change-Id: I2c1a4d32adbf5c148a02819af5e318b4641c4e66
Reviewed-on: http://review.typo3.org/31631
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>