Annotations

A first step in supporting annotations. This code shows ellipses, arrows an textboxes in the resulting tikz diagram, but fails to align this in the right way with the actual plot.
Two small test diagrams are included:
annotation_01.m shows the improvement, while annotation_02.m shows some problems.

As mentioned in some e-mails, I have written code, that fixes the alignment and shows the annotations at the right place, but this code is based on an older version of the script and still breaks some figures of the acid test. 
A pull-request for the new way of alignment will follow as soon as it works with the new version of the script and does not break too much (if I fail to do so, I will ask for some discussion about it)