Oracle upgrade script to migrate from 1.1.1 to 1.2.0-rc0

[akolotov]

This script is intended to upgrade an existing xDai bridge oracles from the release 1.1.1 deployed through the standard deployment procedure to 1.2.0-rc0. It uses the tokenbridge oracle docker image instead of cloning the git hub repo.

The script performs the following actions:

• update the poabridge service (assumes it is in the default location: /etc/init.d/poabridge) to use a new docker compose environment
• generate the new new docker compose environment to introduce new workers
• pull the new TokenBridge oracle docker image
• link new workers with the new docker image

The instruction to use this script was provided on the TokenBridge forum.

In the future similar script could be provided to simplify the migration process to next releases.