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
Fixed wrong attr type on GapImg.objectLabel

Thanks to Mike Koch for noticing this.
Merge branch 'production'
Improved default logback config
Removed "item playback" functionality.

This was causing problems with the cascading data deletion
and was fun but not totally useful. We can do something similar
but more lightweight later if required.
Removed 'set public' for assessments/del settings

This never really went anywhere and I don't think we'll have
time to do anything useful with this for now.

The underyling entity fields have been kept as they're used to
mark the pre-loaded settings and demo assessments.
Fixed regressed link on "edit delivery" form
Changed MVC exception interception method

Now uses Spring beans rather than servlet filter. Printed details
are now more useful.
Tidied up entity id field names + toString()
Tidied up the HEAD~2 commit slightly.

I've moved the creation of the exception resolver to
the WebApplicationConfiguration so that it can be shared with other
beans.
Merge branch 'production'
Set up error page for the engine webapp
Minor tweak to logback config + exception level