Ready for 1.0-M3
Minor JavaDoc improvemnents
Migrated from log4j to logback.

There will be further log configuration changes later...
I want to divorce the qtiworks-engine logging config from the
webapp completely so that people can set up their own logging.
Set hibernate.id.new_generator_mappings=true

This wasn't set before and I didn't see the log message about
it until I pruned the logging in the last commit.
Fixed bug in FileSandboxResourceLocator

This was not handling paths with special characters in them correctly.
The CustomUriScheme class has been enhanced to deal with both raw
and decoded paths in a more specific fashion to help with this.
Externalised log configuration

I have added a ServletContextListener to search for an external logback
configuration file, specified via an initialisation parameter. If
nothing is specified then a revised and much simple/quieter default
configuration will be used.  This will allow people to control their
logging more carefully and easily.
"Fake user ID" now set dyanamically
Minor refactor to instructor authn filters

This now configures itself dynamically, so web.xml
no longer needs to be filtered during the build time.
Minor JavaDoc tidy