* added function to check if meta-field is defined by a plugin
* hide un-defined meta-fields in details view
* fix default charset = utf8mb4
* remove broken DATABASE_VERSION fallback
* split off upgrade infos for version 1.x
* fix page out of range #4279
* calc once, then re-use
* prevent invalid theme switch
* allow to turn off weekly-quick-entries by permissions
* remove 00:00 from date-times that likely do not need a time
* fix datepicker out of window
* 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
* open "create new project/activity" form in modal
* re-use action translation for create action title
* do not pre-select first customer in list - fixes#1828
* sort user preferences in sections for better visual grouping
* show comment date only in hover of user avatar
