[xbus-fullenv] Add a 'restore' setting entry
Created originally on Bitbucket by cdevienne (Christophe de Vienne)
This entry would specify a pg backup file to restore before running xbusd.
Some extra options would be needed to determinate:
- what to do with existing actors/accounts/pipelines/processes
- if a db migration is needed/allowed. If the database is pre 3.0.0-beta.14, the database version could also be set as an option so xbus-fullenv knows which scripts should be applied.