Hardcoded domain delimiter in resource name v3.

Hi,

Currently the delimiter to specify domain for keystone v3 in resource's
name is hardcoded to "::". This impede me from using a name with "::"
in it while they are perfectly valid name in openstack[1]

To solve this we could add a property to the resource. This would
enable the user to use weird name with "::" in it and assign a "/" (for
instance) to the delimiter property:

    Keystone_tenant { 'foo::blah/bar::is::cool': delimiter => "/", ... }

 bar::is::cool is the name of the domain and foo::blah is the project.

[1]:
http://lists.openstack.org/pipermail/openstack-dev/2015-September/074232.html
by the end.