Added support for the infrastructure for on demand access/create the

server connection.

The BaseDriver and BaseConnection are two abstract classes, which allows
us to replace the existing driver with the currently used. The current
implementation supports to connect the PostgreSQL and Postgres Plus
Advanced Server using the psycopg2 driver.

web/pgAdmin4.py

@@ -41,9 +41,11 @@ if config.SERVER_MODE is True:
 
 # Check if the database exists. If it does not, tell the user and exit.
 if not os.path.isfile(config.SQLITE_PATH):
-    print "The configuration database %s does not exist.\n" % config.SQLITE_PATH
+    print "The configuration database %s does not exist.\n" \
+            % config.SQLITE_PATH
     print "Please run 'python %s' to create it.\nExiting..." % os.path.join(
-        os.path.dirname(os.path.realpath(__file__)), 'setup.py')
+            os.path.dirname(os.path.realpath(__file__)), 'setup.py'
+            )
     sys.exit(1)
 
 ##########################################################################
@@ -55,6 +57,8 @@ app = create_app()
 
 if config.DEBUG:
     app.debug = True
+else:
+    app.debug = False
 
 # Start the web server. The port number should have already been set by the
 # runtime if we're running in desktop mode, otherwise we'll just use the
@@ -70,6 +74,6 @@ else:
     server_port = config.DEFAULT_SERVER_PORT
 
 try:
-    app.run(port=server_port)
+    app.run(port=server_port, use_reloader=(config.SERVER_MODE and app.debug))
 except IOError:
     app.logger.error("Error starting the app server: %s", sys.exc_info())