Modified setup_edifice.py to more-or-less cleanly support PostgreSQL 9.0-9.2 with PostGIS 2.0.x+ support.

Significant changes include:

1. A distinction between '--init' (which creates a template PostGIS database,
'base_postgis', using the postgres superuser) and '--create' (which is to be run afterwards and
does not require the postgres superuser). Added optional --bindir, --user, and --database
flags to specify location of Postgres binaries, edifice database username, and edifice
database name. See the README.md (or --help).

2. Replaced all calls to os.system with the subprocess library which allows for cleaner
invocation on files with spaces and other shell ephemera.

3. Replaced os.system call to unzip with the zipfile library.

4. TODO: Actually do more than build the db structure and try to import the shapefiles.
We also currently get some warnings/errors if we try to import the entire
init_scripts/edifice_initialization_script.sql file; check w/ Cory to figure out what
those might be about.