Fix error reporting on node name collision

Signed-off-by: martin f. krafft <madduck@madduck.net>
Use "init" as directory index

The docs mentioned 'init' (which is consistent with Salt and Python), but
somehow I made that 'index' in the code.

Signed-off-by: martin f. krafft <madduck@madduck.net>
Also mangle relpath during inventory enumeration

Signed-off-by: martin f. krafft <madduck@madduck.net>
Beef up the example inventory

Signed-off-by: martin f. krafft <madduck@madduck.net>