Added convenience methods to (Abstract)Value

Added Signature methods, and methods for checking baseTypes
and cardinality
Fixed bug in response processing

If RP is invoked without binding response values, then
endAttemptInteraction response values were left NULL, causing
a ClassCastException. RP now sets these to false if no binding
occurred earlier.
Minor refactoring to XML reading APIs

* Deleted the ModelRichness idea as it was never fully implemented
* Split resolution code in AssessmentObjectManager into a separate class
s/(AssessmentObject)Manager/$1XmlLoader/g

This name is more descriptive. Also moved this into the
*.reading package with the rest of the XML reading classes
Did some tidying/improvements to XSLT classes
Fixed bug in unmarshalling of File values
Merge branch 'production'
Fixed missing fileName when storing FileRespData
Improvement to handling of uploadInteraction
Fixed handling of very long contentType fields

* Increased column size to 256
* Strings longer than this are now trimmed down
Fixed MathML schema location
Tidied up and documented extension API slightly

NB: The 'Lifecycle...' classes are now called 'JqtiLifecycle...'.
Fixed missing test OP checks when pooling
Added 'not null' check for JExtMgr in AbsValCtxt