man5: Moved some option descriptions to section doamin,
accordingly to commit 4ff0fa3ba0fa. Added a brief explanation of which
settings will be applied in which situations.
# All parameters are described in pgsql_table(5) / PGSQL PARAMETERS
#
# The hosts that Postfix will try to connect to and query from.
hosts = localhost
# The user name and password to log into the pgsql server.
user = postfix
password = some_password
# The database name on the servers.
dbname = mailsys
# The SQL query template used to search the database
query = SELECT destination FROM postfix_alias WHERE address='%s'