Implement initial support for tcmu-runner and org.kernel.TCMUService1
Implement initial support for tcmu-runner and org.kernel.TCMUService1

Instead of having a generic "user" backstore, create backstores for
each type of user backstore, as enumerated via the org.kernel.TCMUService1
DBus interface.

The name of each is prefixed with "user:" for clarity.

Extend "create" to check arg count matches expected for each user
backstore, and include user backstore arg parameters in help for the
create command.

Signed-off-by: Andy Grover <b7d524d2f5cc5aebadb6b92b08d3ab26911cde33@redhat.com>

cloud4life/targetcli-fb,cvubrugier/targetcli-fb,agrover/targetcli-fb