* MM-31356: Add a minimum required version check for Postgres
To keep conformance with our failing fast and obvious philosophy,
we add a check to prevent Mattermost server from starting
if the postgres version is below 10.0.
This gives customers a chance to upgrade their database before upgrading
their Mattermost version, than to run into weird compatibility issues
after they have finished the upgrade.
https://mattermost.atlassian.net/browse/MM-31356
```release-note
NONE
```
* fix lint errors
* Use a function to pretty-print version string
* rectify comment
c54b262351