Fix static group list indices in selection prompt

In 4.6, the list was zero-based, and this is what the selection parser
uses when resolving numeric group references, so it should still be.
Also the list shown by various functions in index.c is zero-based.
The printing code had been inadvertently changed to one-based in cleanup
of the handling of group names within the selection code.

Fixes #1506

Change-Id: I9a573b921802d2276e3bdb653359a961c90ff29a