Explicit listing of Glance policies in json file

Most OpenStack components do list their policies in their policy.json but not
Glance. It will let user directly know what options is available to them.
Previously non-listed policy do follow the default rule now.
List of available policies have been taken from Developer Guide page :
http://docs.openstack.org/developer/glance/policies.html#constructing-a-policy-configuration-file

Closes-Bug: #1254461
Change-Id: I833db8385c2d3e8962a9c19b77c94d962eac475e
Merge "Explicit listing of Glance policies in json file"