The users can now be dumped and loaded as JSON objects. This allows easier
parsing and handling of users while still retaining the possibility to
manually edit the output. Added tests for dumping and loading the JSON
form users.
Also fixed a deadlock in Users::remove() where the same lock was acquired
twice and a faulty test case where failed authentication was expected to
work.
The type of the user being created is defined at creation time. This
allows the creation of basic users.
Although the users can be created internally, they cannot yet be created
via maxadmin or the REST API.
The refactored interface is now in use. The only module that used it
directly was the CDC protocol module. This should probably be changed so
that it uses the adminusers interface instead of the users interface
directly.
