Add templates support

[mpsonntag]

With the addition of templates.g-node.org there is a second option to import usable odml files.

Either add support in the current terminologies wizard to import templates or add a dedicated templates wizard.

As an option it might make sense to add an additional first page to the current wizard where the user can decide whether to work with a template or a terminology since the handling is slightly differently and might diverge even further.

[mpsonntag]

A dropdown with fixed selectables would probably be the best option.