* adds model and form mixin for PIK
* integrates mixins for compensation, ema and ecoaccount
* adds migration files
* extends API
* extends API test data
* adds is_xy fields to compensation, ema and ecoaccount reports
* adds is_pik information to detail views
* adds/updates translations
* adds tests for team sharing
* extends the API for team sharing support
* adds shared_teams property shortcut for ShareableObjectMixin
* adds full support for team-based sharing to all views and functions
* simplifies ShareModalForm
* adds/updates translations
* adds team sharing field to share form
* splits sharing logic into user based and teams based
* adds TeamAdmin for admin backend
* adds validity check on Team name -> only unused names shall be valid
