Added oo-admin-ctl-geo script to manipulate geos/zones

Modified oo-admin-ctl-district to handle geo/zone during node addition

Fix district test cases

Added man pages for oo-admin-ctl-geo

Updated oo-admin-ctl-district man page with goe/zone details

When geo/zone enabled, prefer gears in a group instance to belong to different zones within the current geo
Move serializable_hash_with_timestamp method to model_helper.rb