decouple sql debug from debug and implement a verbose

Would be useful to decouple sql debug from normal debug. Also sqlalchemy supports the following debug levels using the echo parameter to create_engine:

1) echo=false (supposed to be identical to echo set to None, the default but doesn't behave well on version 0.6.4.3 of sqlalchemy
 so I've found the to be safer, see http://<email address hidden>/msg25071.html
for more detail. Glance is using echo=false , works fine on later sqlalchemy but problems on earlier version.

2) echo=true - the same as setting the the loglevel=debug i..e. logs sql statements

3) echo='debug' - returns result set as well as logging sql statements, currently not used by glance

Would be useful get 3) for glance using a sql_verbose option and I think because of 1) we should use the default rather than echo=false as this works better on older versions of sqlalchemy .

I will attach a patch which does the above