Fix the udp api to use json.UseNumber()
Add backfill option to into clause parser

Signed-off-by: Dhammika Pathirana <dhammika@gmail.com>
Check backfill flag in continuous query

Signed-off-by: Dhammika Pathirana <dhammika@gmail.com>
Add continuous query backfill integration test

Signed-off-by: Dhammika Pathirana <dhammika@gmail.com>