views.py:
- add_visit_type:
   - don't use @permission_required decorator, check against project instance via has_add_permission method
- edit_visit_type:
   - don't use @permission_required decorator, check against project instance via has_modify_permission method
urls.py:
- remove unused route site_compensations

views.py
- remove unused view view_site_compensations
- view_samples, view_sites:
   - avoid custom decorator require_project_or_site_view_permission, do perm checking in view code to avoid double queries
views.py
- avoid custom decorators, do perm checking in view code to avoid double queries