Put postgis_topology_scripts_installed() in topology schema (#2502)

This was the only topology signature installed in the default schema.
The postgis_full_version() function is updated to find it there.

git-svn-id: http://svn.osgeo.org/postgis/branches/2.0@12014 b70326c6-7e19-0410-871a-916f4a2858ee