Added rendering support for pV/@index
Minor logic tweak to CandidateSessionStarter...

We now check to see whether the candidate already has
a non-terminated session on the given Deliverable. If there
is one, we'll reconnect to it (or the most recent one). Otherwise
we'll create a new session. This should help with situations
where the candidate clicks on a start button twice, or something
like that.
Belated mark of DEV20, slipped out earlier
Fix to default value for maxChoices in 5 i'actions

I discovered that the default value for maxChoices changed from 1 to 0
somewhere between drafts 2 and 13 of the QTI info model for
choiceInteraction, hotspotInteraction, hottextInteraction,
positionObjectInteraction and selectPointInteraction.

These were very poorly described in the changes document. Chances are
there will be similar issues elsewhere
Ready for 1.0-M2
Merge branch 'master' into test_implementation
Ready for 1.0-DEV21