Change how db auth is done for dev and test.

Not specifying a username and password means we can fall back to ident
based auth.  This relies on a postgres role with createdb permissions
existing for the user running.  This has been configured on the dev VM
and on CI.

This change also updates the jenkins script to drop the database before
each run to ensure a clean state.
Failing tests for path reservation
Add factory_girl
Add Reservation model
Refine json representation of Reservation
Disable Rails’ automatic JSON parsing.

Causes problems - see comment on disable_params_parser.rb for details.
Implememnt reservation put action.

This doesn’t yet check for conflicts, but it does cover all the other cases.
Prevent reserving path claimed by another app.