Eco Account deduction

* adds deductable_surface to EcoAccount model to provide an easy way to change the deductable amount from an account -> depends on external funding e.g. with AktionBlau or similar
* adds overview of deducted and deductable volume to detail view
* adds check to eco account model, so the deductable_surface can never be larger than the total amount of after_state surface sum
* adds german formating for python logic based number formating
* adds/updates translations

compensation/templates/compensation/detail/eco_account/view.html

@@ -33,6 +33,7 @@
                     <tr>
                         <th scope="row">{% trans 'Available' %}</th>
                         <td class="align-middle">
+                            {{obj.deductions_surface_sum|floatformat:2}} / {{obj.deductable_surface|floatformat:2}} m²
                             {% with available as value %}
                                 {% include 'konova/custom_widgets/progressbar.html' %}
                             {% endwith %}