pgAdmin 4 commit: Update the setup script and config database to handle

Update the setup script and config database to handle versioning.

This allows us to update the configuration database schema as needed,
and use the setup script to update it to the current version.

NOTE: Existing databases will need to be recreated once following
this commit. It doesn't seem worth handling the "upgrade from v0"
case when I'm probably the only active developer right now.

Branch
------
master

Details
-------
http://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=7f68d6fcedefa235d19e37d7566078fe31095eef

Modified Files
--------------
web/config.py | 4 +
web/pgadmin/settings/settings_model.py | 51 ++++++++---
web/setup.py | 147 ++++++++++++++++++++++----------
3 files changed, 144 insertions(+), 58 deletions(-)