WiP on selectable mosaico templates.
TODO: Make files always point to trusted URL, such that we don't have to rebase them. They are public anyway. The same goes for mosaico endpoints: /mosaico/templates and /mosaico/img
Reworked routing and breadcrumb mechanism. It allows resolved parameters in paths, which allows including names of entities in the breadcrumb.
Secondary navigation which is aware of permissions.
Custom forms list
Updated DB schema (not yet implemented in the server, which means that most of the server is not broken).
- custom forms are independent of a list
- order and visibility of fields is now in custom_fields
- first_name and last_name has been turned to a regular custom field
