Payments add modal form

* adds help texts to add payment form
* adds removing button for payments
* refactors user fetching into BaseForm
* adds generic RemoveModalForm which is intended to be used for every modal form which shall remove something
* adds translations
* removes unused html
* prepares payment amount field to be able to process german inputs like '1.000,50' which is not the international default

compensation/admin.py

@@ -41,7 +41,9 @@ class PaymentAdmin(admin.ModelAdmin):
     list_display = [
         "id",
         "amount",
-        "due_on"
+        "due_on",
+        "created_by",
+        "created_on",
     ]