App: Grails forces a comma into i18n numbers causing URL errors.

This fix explictly casts the id of the IDPSSODescriptor to a String.
This ensures the Grails GSP engine renders it directly without
molesting the formatting on the way through which should be the
default anyway.

References #143.
Merge pull request #143 from ausaccessfed/bugfix/#143-comma-filter-policy-id-greater-than-4

Attribute filter policy URL has a comma in the ID number for 4 or more digit numbers