Good first attempt at the implementation section.
Next stop: evaluation/experiment. This may require some coding etc. as well...

* [APPROX] Definition names were missing.
* [BIB] Added several references to implementation-related literature.
* [DEB] Empties the TODO file, using Github issue tracking for that now.
* [FIXPOINT] Extended the figure caption a bit.
* [IMPLEMENTATION] Wrote a first version of the implementation section. Only very little remains to be said about this.
* [SC] Make sure \texttt{} is {\small} everywhere.
* [SC] Removed misplaced BiBTeX files.
* [SC] Removed IOTW code for ipairs. This was no longer used.