Link chooser Working!
Merge branch '1.6-link-choosers' into 1.6
Allow admin to visit and view pages in maintenance mode

Updated CroogoAppController.php to allow users with an admin role to visit and
view pages in maintenance mode.
Maintenance IP Whitelist

Setting `Site.ipWhitelist` added. IP addresses can be whitelisted, enabling
clients from that ip address to view website regardless  the site status.

The appropriate Setting key also added to SettingData.php
Merge branch 'pr-231' into 1.6

Closes GH-231