Model representation and XML reading support for core apipAccessibility features
Adding serialization support for APIP accessibility structures, along with capabilities for controlling the output XML namespaces via profiles. Sane ISO-compliant time input and output for audioFileInfo and videoFileInfo made possible by the addition of a dependency on joda-time.
Improving validation of content links. Firming up parent/child relationship typing for accessibility elements.
Adding stylesheet and apipAccessibility to the elements which now can contain these in QTI 2.1 Final: rubricBlock, templateBlock, feedbackBlock, and modalFeedback.
Merging upstream improvements.
Correcting overlooked merge adjustment: the movement of ForeignElement up a namespace-level.
Merge branch 'master' of https://github.com/davemckain/qtiworks
Added drawingInteraction xsl and rendering
Merge branch 'master' of https://github.com/ZackPierce/qtiworks

Conflicts:
	qtiworks-jqtiplus/src/main/java/uk/ac/ed/ph/jqtiplus/utils/QueryUtils.java
	qtiworks-jqtiplus/src/test/java/uk/ac/ed/ph/jqtiplus/reading/QtiObjectReaderTest.java
Calculator tool

Implementation of calculator tool. Also refactored GeometryDrawing into
a custom interaction