Clean up OdtDocument cursor position tests

Make OdtDocument cursor position tests more granular in how they are reported. This makes it easier to troubleshoot individual failing tests as the individual test is more specific.

* Extend core test runner to cope with test names containing angle brackets
* Verify the number of steps vs. expected number of cursor positions
* Remove doc length check for non-changing variables
* Report one test per cursor position document fragment
I was thinking that the length check was unnecessary the second time... but that logic is not re-assuring me still. I've reverted this part, and actually made it so the length is re-measured each time instead (i.e., fixing the check to be useful).