Updated M4->M5 schema migration after DEV29 rel.

This now incorporates all of the changes from DEV26->DEV29.
Updated to Spring 3.2.3
Removed old "finished" and "model solution" notes

This duplicates the information shown in the status indicator
and isn't styled very well. I'll leave this out for now; we can
maybe reintroduce something better in future.
Change to testPart feedback

In LINEAR navigation mode, I'm now only showing sections & items that
have actually been entered. This seems like the right approach,
especially if there are branchRules and preConditions within the
testPart, otherwise it will give too much away about the structure
of the testPart.
Minor Javadoc improvements