Add support for creating and migrating Geo database and help configure Geo replication

To make a Geo node secondary, add to /etc/gitlab/gitlab.rb:

geo_secondary_role['enable'] = true

We also have a primary role:

geo_primary_role['enable'] = true

By enabling primary or secondary role we also enable most of the replication changes that doesn't require extra input from the user

Fixes #2073 (closed)