It took a lot of time to produce a testcase for this as the test
config was setting srid to 4326 but not changing geom column name
thus all tiles fetched by tests returned blank (ouch!)
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
