Adds a man page for CLI's IP address group command.

Fix MN-1078

Change-Id: Ib851e1e341bbe9e73aecb1711efdc8d4ea07d86c
Merge pull request #99 from midokura/dev/tomohiko/ipa_group_cli_man_v1.3/20140124

Adds a man page for CLI's IP address group command.