Add triggers for shapefile reprojection

Adds two new tables, with utm_ prefixes, to store shapefile data
(boundaries and demographic data) in the local UTM projection. These
tables can't be managed via the Django ORM because the SRID is set
dynamically upon data import. Adds triggers so that inserts into the
Django model tables result in inserts of reprojected geometry data into
the appropriate utm_* table. The foreign keys cascade so delete triggers
aren't necessary.
Set UTM SRID for Shapefile data in GeoTrellis.

As part of the GTFS import process, GeoTrellis will update the SRID on
the utm_datasources_boundary and utm_datasources_datafeature tables.
No data is reprojected at this stage; that happens via insert / update
triggers when Shapefiles are uploaded.
Fix incorrect fieldname in error handler
Don't allow uploading shapefiles until GTFS exists

This is necessary because otherwise UTM reprojection may not work
because the GTFS feed's UTM zone isn't defined.
Add log output to provision script.
Turn off psql pager during provision

This breaks Travis by waiting for user input during the build.
Add comments after review.
Merge pull request #88 from WorldBank-Transport/feature/reproject-shapefiles

Reproject shapefiles