improve(repo) ignore .sass-cache
fix(grunt) fix the copy target for styles
improve(grunt) use bower for dependency management
improve(grunt) use `less`  to compile CSS
improve(grunt) use `less`  to compile CSS
improve(grunt) laverage bower package managment
improve(grunt) move the assets/vendor/camunda-common scripts to app/common

to keep the vendor folder strictly reserved for bower components
improve(grunt) remove the CSS files located in assets/css

the CSS are compiled from LESS files located in assets/styles
improve(grunt) ignore some backup directory
Merge branch 'CAM-1712-grunt' of github.com:camunda/camunda-bpm-platform into CAM-1712-grunt

Conflicts:
	webapps/camunda-webapp/webapp/Gruntfile.js
	webapps/camunda-webapp/webapp/package.json
improve(grunt) use the `newer` task
improve(grunt) use the `newer` task
improve(grunt) attempt to solve dependencies with bower components