rpm packaging and standalone tests

*     packaging: add rpm building support

*     runtests.sh: set up a new postgresql cluster and run tests there
    
This allows running tests without installing plproxy and should not conflict with any other PostgreSQL instances.  There are a couple of hacks in runtests.sh to work around limitations in installing extensions from outside the global postgresql share directory.

Also reformatted all connection strings in existing test cases to set the target hostname as the first field so we can rewrite it when running tests.