refactor(cockpit): add multi-tenacy + various improvements

multi tenacy
- add a servlet filter that serves cockpit from /app/{engineName}/ paths
- refactor filter infrastructure
- add multiple two more engines to dev setup
- add client side drop down to choose current engine
- current engine is read from url
- add replace support for :engine with current engine in Uri#appUri

other changes / improvements
- update main index.html to use absolute path rather than relative one
- migrate message structure from Errors to Notifications
- implement resource resolving

other cleanup being done
- remove unused root controller
- fix spacing all over projects
- fix usage of ' in place of " in may files

Closes CAM-879