#101 Team sharing form

* 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

compensation/forms/forms.py

@@ -400,7 +400,7 @@ class NewEcoAccountForm(AbstractCompensationForm, CompensationResponsibleFormMix
                 comment=comment,
                 legal=legal
             )
-            acc.share_with(user)
+            acc.share_with_user(user)
 
             # Add the log entry to the main objects log list
             acc.log.add(action)