Engine web.xml is now schema valid

Some elements were not listed in the correct order. These are fixed
here.
Updated JSP version (2.1) and fixed NS & schema
Minor JSP fixes after running through validator
Minor improvement to MVC exception resolver

This no longer logs CandidateExceptions, as these will have already been
logged by the CandidateAuditLogger.
Minor improvement to MathAssess glue

* Unexpected failures in the SnuggleTeX up-conversion process are now
wrapped in a better Exception, allowing the original input to be logged
to help fix SnuggleTeX.
* Renamed some methods in the MathAssess packages to use the newer
naming conventions that were introduced earlier in the year when tidying
things up.
Fixed some tabs. Had crept in working on laptop.
Removed vestigial ref to 'ltipage' taglib
Fix for #46: Added default template for <param>

This was missing from the default XHTML element handling template in
qti-common.xsl. (It wasn't noticed before as <param>s inside items are
handled by a special template in item-common.xsl that deals with
template variables.)