Add TimescaleDB support using global hypertables for PostgreSQL

[Viishveesh]

This PR introduce the TimescaleDB support for postgreSQL.

• dbqury.py: Updated query generation functions to support PostgreSQL with global hypertables.
• dbconn.py: Modified the PostgresDBConn to support TimescaleDB.
• create_tables.py: Added logic to create the global aggregate table.
• decoder.py: Updated the decode_msgs function to support the global hypertables for the postgresql.
• sqlfcn.py: Updated the file to use the global logic for the postgresql and the monthly logic as it is for the sqlite.

Added test cases to check the updated functionality of the postgresql. Also, I have added the sql code to create the global hypertables with the chunk size of the 7 days.