* writes test for sharing using the API
* fixes bug on frontend form where an exception occured on generating a new API token if no token existed, yet
* adds permission constraint (default group) for using the api in general
* fixes default-group-only behaviour for sharing-API, so users can only add new users and not removing them, as long as they do not have any other group membership like registration or conservation office
* changes 'ksptoken' to 'Ksptoken' to match CGI standard for http header keys
* adds functionality for withdraws from eco accounts in detail view of interventions and eco account as well
* adds get_surface() method to AbstractCompensation class to provide a simple getter for a sql calculation
* adds get_surface_withdraws() method to EcoAccount class to provide a simple getter for a sql calculation
* renames some routes to match coherent rout naming
* adds logic check on NewWithdrawForm
* renames templates/table directory to templates/form, since there are form-table templates inside --> more clarity
* adds new autocomplete routes to konova/urls.py for Interventions and EcoAccounts
* adds/updates translations
* adds/updates template comments
* updates requirements.txt
* adds user/includes/contact_modal_button.html for calling contact data of a user
* adds user contact modal to intervention detail view
* adds translations
* 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
