[CBAM.SQL.PostgreSQL] Add actual support for reading values from backend in binary format

[stazz]

Currently, the CBAM.PostgreSQL.Implementation protocol always tells the backend to send its data in textual format. This is because the bind message is sent before describe, which I think is because we are using portal instead of statement (the batch execution uses statement, and it sends those in different order).

It should be investigated as to how properly allow users to active binary read functionality. One way could be via configuration, in protocol section, where some related information already exists now.