* prevent too long values for user preferences
* add chart value 0 to y-axis if last value > 0, to always display the zero line (project details)
* add user-preferences to invoice hydrator
* DateTime vs DateTimeInterface
* simplify permission config
* fix query for teamleads limiting to only selected teams not possible
* improve report visibility
* fix timesheet duration, which breaks validation
* added contributing section in README
* do not allow to change project for existing activities - fixes#2576
* bump theme version to fix FOSUserBundle dependency
* use entity color instead of inherited one - fixes#2200