Initial commit into the new Git repository.

The old history contained some privat data, that could not be published.
Do not depend on pdftk.
Use write() instead of print so that no newline is added to the ids file.
Handle "recognize" correctly, if no images have been imported yet.
Minor changes in the README.
Add .gitignore file.
Lower the threshold.
Fix the matrix multiplication

For whatever reason multiplying cairo matrices with '*' does not work for
me anymore. So it is now replaced with an explicit .multiply().
Fix the test script.
Removed some debug graphics.
Add test data.
Fix the spinbutton, and with this the stepping with the next button.

This commit changes some more stuff, because of glade and also removes some
commented out code.
Add a couple of todo items.
Simplify the tiff reading code a bit, by letting libtiff rotate the data.
Fixed a warning by casting the bounding box of the clip to be integers.
Added a fast path to stamp the sheets using pdftk.

The code now will make use of pdftk if it is available to put the
questionnaire into the background of the marks that are generated by
python. This is much faster than using the python PDF library.

pdftk is still not needed. If it is not available the slower code path
will still be used.
Output more information during stamping about pdftk calls.
Small speed improvements in stamp.py.

Well, it probably was already fast enough, but what the heck :-)
Refactor stamping.

The stamping code now needs either pyPdf or pdftk. Using pdftk is much faster,
but pyPdf is still supported as a fallback mechanism.
Removed a useless try block.