[GRASS-dev] new i.group flag

Hi,

I have just added a -g flag to i.group to list maps in simple parseable
form (map@mapset, one per line). This should make bulk compulations on
imagery groups simpler to script.

two new fns added: I_list_group_simple() and I_list_subgroup_simple()

also fixed a bug: listing subgroup maps would actually list all maps in
the group.

Hamish