Re-introduces use of the redis "privacy" hash key as an additional
security measure for requests that do not involve PostgreSQL access.
Accessing private table styles is tested with this commit.
Accessing private table metadata or infowindow is _not_ tested,
but should also be fixed now.
If the request is authenticated (with map_key) then we log as the
database owner, otherwise we log as the default user.
The default user is now "publicuser" by default.
Raises dependency on Windshaft to 0.4.9+, to get the grainstore
version allowing override of database username.
Add test for req2params function, particularly authentication,
Add test for authenticated / unauthenticated access
Sandro Santilli