Allow to connect any of the database using its OID using the connection

manager, once the connection to the maintenance database has been made,
because - we will have did (i.e. Database OID) most of the time for the
any node, and not its name as identifier.

This will allow us to work directly with OID, and we will not need to
bother about renaming of the database name.

web/pgadmin/utils/driver/psycopg2/__init__.py

@@ -162,6 +162,19 @@ SET bytea_output=escape;
 
                 return False, res
 
+            status, res = self.execute_dict("""
+SELECT
+    db.oid as did, db.datname, db.datallowconn, pg_encoding_to_char(db.encoding) AS serverencoding,
+    has_database_privilege(db.oid, 'CREATE') as cancreate
+FROM
+    pg_database db
+WHERE db.datname = current_database()""")
+
+            if status:
+                mgr.db_info = dict()
+                f_row = res['rows'][0]
+                mgr.db_info[f_row['did']] = f_row
+
         if 'password' in kwargs:
             mgr.password = kwargs['password']
 
@@ -393,6 +406,7 @@ class ServerManager(object):
         self.role = server.role
         self.ssl_mode = server.ssl_mode
         self.pinged = datetime.now()
+        self.db_info = dict()
 
         for con in self.connections:
             self.connections[con]._release()
@@ -421,11 +435,44 @@ class ServerManager(object):
             return int(int(self.sversion / 100) / 100)
         raise Exception("Information is not available!")
 
-    def connection(self, database=None, conn_id=None, auto_reconnect=True):
+    def connection(self, database=None, conn_id=None, auto_reconnect=True, did=None):
+        msg_active_conn = gettext(
+            "Server has no active connection, please connect it first!"
+            )
+
+        if database is None:
+            if did is None:
+                database = self.db
+            elif did in self.db_info:
+                database = self.db_info[did]['datname']
+            else:
+                maintenance_db_id = 'DB:' + self.db
+                if maintenance_db_id in self.connections:
+                    conn = self.connections[maintenance_db_id]
+                    if conn.connected():
+                        status, res = conn.execute_dict("""
+SELECT
+    db.oid as did, db.datname, db.datallowconn, pg_encoding_to_char(db.encoding) AS serverencoding,
+    has_database_privilege(db.oid, 'CREATE') as cancreate
+FROM
+    pg_database db
+WHERE db.oid = {0}""".format(did))
+
+                        if status and len(res['rows']) > 0:
+                            for row in res['rows']:
+                                db_info[did] = row
+                                database = db_info[did]['datname']
+
+                        if did not in db_info:
+                            return False, gettext(
+                                "Coudn't find the database!"
+                                )
+
+        if database is None:
+            raise Exception(msg_active_conn)
 
         my_id = ('CONN:' + str(conn_id)) if conn_id is not None else \
-                ('DB:' + (str(database) if database is not None else \
-					self.db))
+                ('DB:' + str(database))
 
         self.pinged = datetime.now()