Merge pull request algorand#1588 from gmalouf/protocol-update-sync

Consensus: v39 protocol support via go-algorand-sdk

Use INDEXER_DATA throughout the entrypoint script in docker (algorand…

…#1583)

Use the env var everywhere.

Add gpg signature to checksum file. (algorand#1573)

Initial commit of release

Update submodule to 3.13.3 (algorand#1427)