* adds UserActionLogEntry model to user/models.py
* wraps user and timestamp info
* can be extended for more information in the future
* refactors all filtering and accessing on values
* refactors templates/table.html into templates/generic_index.html
* adds DummyFilterInput as do-not-render-widget
* hardens combination of q filter and other filters on index view rendering
* 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
* adds modal form for adding payments
* generalizes generic_table_form.html for table-form-like usage in modal_form.html
* adds css enhancements for focused input fields
* adds BaseModalForm as specification to BaseForm, which inherits the BSModalForm class as well
* adds translations
* adds hint for empty map in case of missing geometry
* adds empty geometry workaround, so openlayers is rendered without digitalization tools
* adds translations
* adds related object overview in detail view
* adds comment field to payment model for 'Verwendungszweck'
* simplifies intervention urls
* adds translations
* adds (WIP) detail view for interventions
* renames typo in conservations_file_number to conservation_file_number
* adds simple has_access check for intervention objects for given users
* renames occurences of "Registered" to "Recorded" (verzeichnen)
* adds an informing message for detail view of intervention objects which are not editable for a user
* adds GeometryAdmin
* adds fallback DEFAULT_SRID for Geometry model
* adds translations
