Updated dependency details

* Updated versions of Guava and XMLUnit (neither currently in use)
* Added note to avoid using commons-lang & commons-io
Migrated SnuggleTeXValidationTest to JUnit 4
Minor fixes to refactored unit tests
Added XSLT caching control to deployment settings
Aardvark manager now ported and kind of working
Removed aardvark-backend module

This has now been refactored into basis for new unified webapp module
Ported webapp init gubbins from QTIWorks
Should have been in HEAD~3
Tidy up after last few commits
Renamed aardvark-aardvark2 -> aardvark-webapp
Added basic machinery for runnable webapp
Added more debug logging to ThreadLocalCleaner
Removed debugging code added yesterday
Added bean config for the Processing Engine
POM updated to include servlet deps
Removed 'passwordDigest' from User object
Updated .gitignore to exclude webapp log/ctx files
Tidied up naming of StylesheetResourceReader
Fixed a couple of bugs in the Processor test suite
Merged & trimmed ph-commons modules