Beefed up Features support: when adding a node type to a Feature, add the subpages for it, and vice versa

Issue #1548500 by andirez, BrockBoland: Module will not install due to hook_requirements() dependency in .install file

Check for ctools in appropriate places. Upgrade Fields to use plugins (still need to update for Views)

Issue #1447992 by Argus, BrockBoland: Invalid argument supplied for foreach() in _node_subpages_get_field_value()

Issue #1447992 by Argus, BrockBoland: Invalid argument supplied for foreach() in _node_subpages_get_field_value()

Cleaned up _node_subpages_get_field_value() to show all values for a field, and better handle notices for unset indexes

Fixed the path to content type management. Cleaned up several notices for unset variables/indexes. Some other D7 API changes

Load subpages by weight, so that they are ordered correctly, and don't return NULL for a page output (results in a blank page if you do that)