Regression test for Elan to GrAF conversion

[pbouda]

There was a bug in the Elan parser that put integer values in an internal data structures that could not be serialized by the GrAF parser. Here is the commit that fixes the problem:

faef6d4

It was presumably caused by the creation if "missing" timeslots. There is a demo file available on SkyDrive/Nordhoff. Write a regression test for this problem.