Implemented ErrorWidget + refactoring of widget's templates and widget's js classes
Merge branch 'master' of github.com:Schibsted-Tech-Polska/stp.rtm

Conflicts:
	module/Dashboard/src/Dashboard/Controller/LongPollingController.php
	module/Dashboard/view/dashboard/dashboard/widget/build-widget.phtml
	module/Dashboard/view/dashboard/dashboard/widget/error-widget.phtml
	module/Dashboard/view/dashboard/dashboard/widget/messages-widget.phtml
	module/Dashboard/view/dashboard/dashboard/widget/number-widget.phtml
	public/js/dashboard.js
	public/js/widget/Widget.js
Corrected typos after merge.
Refactored styles of widget's containers + corrected typos in widget's js files