Add documentation for how to upgrade PostgreSQL
Currently the minimum supported version of PostgreSQL is 9.6 but both 10, 11 and 12 exist and so we really should have some documentation on how to upgrade both PostgreSQL data and binaries.
Currently the minimum supported version of PostgreSQL is 9.6 but both 10, 11 and 12 exist and so we really should have some documentation on how to upgrade both PostgreSQL data and binaries.