lighten active tab color
update Lessy to v0.1.0
move less files to new Assets directory
add Lessy.JsConcatFilter
add Lessy configuration
add alternative group name to flash message, create new warning
add additional indices to speed up queries
throw an UnauthorizedException if the session of an ajax call expired
ignore empty translation fields on data submission
add hard coded route types, add validation rule to check uniqueness
temporarily backup buttons
add bottom_body block, remove plugin asset output
add getBackendUrl helper method, update backendConfirmationLink

- backend confirmation links now use a prerendered modal structure that is
  more flexible than the pure "on the fly" modal creation via js
- modals utilize the new bottom_body layout block
several layout/view/ style changes + additions

amongst others:
- new structure for form buttons
- new structure for backend confirmation links
- make use of new button graphics
- shrink aside with to 200px
- add more custom backend errors