fix(cockpit/grunt): add missing less build target
refactor: frontend libraries upgrade

BREAKING CHANGE:
This commit upgrades the some frontend libraries like
- angular.js, now version 1.2.16
- bootstrap, now version 3.1.1, javascript is not used anymore

Due to significant changes in angular.js, you might need to make some changes
to your plugins as described in the migration guide:
http://docs.camunda.org/latest/guides/migration-guide/#migrate-from-camunda-bpm-71-to-72-migrate-cockpit-plugins

Related to CAM-2147, CAM-2157, CAM-2158, CAM-2159, CAM-2160, CAM-2160, CAM-2161, CAM-2162