EMA

* adds Ema model (basically Compensation inherited)
* adds index view for EMAs
* fixes drop-down link bug for menu 'More' in navbar
* refactors some more forms to use process_request()
* adds modified attribute to BaseResource for easy last_modified check
* adds setting of modified attribute in all places where UserAction.EDITED is added to log
* adds EMA_ACCOUNT_IDENTIFIER_LENGTH and EMA_ACCOUNT_IDENTIFIER_TEMPLATE to ema/settings.py
* adds EmaAdmin to ema/admin.py
* fixes wrong title in intervention detail view html for revocations
* adds support for subtitle variable to BaseTable and generic_index.html
* drops next_version attribute from models
* adds/updates translations
* adds default ordering for UserActionLogEntry
   * removes extra ordering in log modal rendering

intervention/models.py

@@ -21,9 +21,9 @@ class ResponsibilityData(UuidModel):
     Holds intervention data about responsible organizations and their file numbers for this case
 
     """
-    registration_office = models.ForeignKey(Organisation, on_delete=models.SET_NULL, null=True, related_name="+")
+    registration_office = models.ForeignKey(Organisation, on_delete=models.SET_NULL, null=True, related_name="+", blank=True)
     registration_file_number = models.CharField(max_length=1000, blank=True, null=True)
-    conservation_office = models.ForeignKey(Organisation, on_delete=models.SET_NULL, null=True, related_name="+")
+    conservation_office = models.ForeignKey(Organisation, on_delete=models.SET_NULL, null=True, related_name="+", blank=True)
     conservation_file_number = models.CharField(max_length=1000, blank=True, null=True)
     handler = models.CharField(max_length=500, null=True, blank=True, help_text="Refers to 'Eingriffsverursacher'")
 
@@ -115,9 +115,6 @@ class Intervention(BaseObject):
         related_name="+"
     )
 
-    # Holds which intervention is simply a newer version of this dataset
-    next_version = models.ForeignKey("Intervention", null=True, blank=True, on_delete=models.DO_NOTHING)
-
     # Users having access on this object
     users = models.ManyToManyField(User, help_text="Users having access (data shared with)")
     access_token = models.CharField(