configure error handling for less with plumber

prevents gulp to quit when an error occurs during less processing
use less for all styles - replaces bootstrap.css + main.css
custom import of needed bootstrap components to reduce css size
remove unneeded angular-ui and angular-bootstrap dependencies
remove all existing js files, external libs and content in index.html - preparation for v2 using angularjs
remove old css styles, add minimal base.less
define main angular module
new data