python - ctl: Add cluster interface.

Log Message:
-----------
Add cluster interface.

This merely ties in all the pg_config, initdb, and pg_ctl interfaces into one
more convenient interface. It also makes use of boss/config to provide
configuration capabilities.

Added Files:
-----------
    ctl/src:
        cluster.py (r1.1)

(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/ctl/src/cluster.py?rev=1.1&content-type=text/x-cvsweb-markup)
    ctl/test:
        cluster.py (r1.1)

(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/ctl/test/cluster.py?rev=1.1&content-type=text/x-cvsweb-markup)