Upgrade local CMS DB to use Postgres 11

[patphongs]

Summary

What we're after:
The CMS postgres databases in our cloud environment is now using postgres version 11. We need to make sure our local environment is running the same version.

Related issues

• Update README, team postgres version to 10.7 openFEC#4332
• Upgrade local eRegs DB to use Postgres 11 fec-eregs#499

Completion criteria

• Local CMS database is running using Postgres V11. Document somewhere for staff to repeat process done already by @fec-jli
• The read.me is updated.

Tech steps or considerations

• Try running both Postgres V11 and Postgres V10.7 locally
• Run local CMS database using Postgres V11

[jason-upchurch]

Thank you @johnnyporkchops and @fec-jli for your help with locating a PG11 .dump file. I moved a copy of the latest one to the FEC CMS DB for devs as part of the PR review.

[jason-upchurch]

working on documenting switching between different versions of postgres in the wiki (openFEC and fec-cms use different versions)