Devel: final cleanup.
I have made some modofocations on devel:
- Changed the noted typos in NumPy and revised Exercise 8
- Bunched the first 3 exercises of Pandas and added Further Resources section
- Added Further Resources to Networks and Scipy notebooks
- Anonymised recordings made by me for the Scipy notebook
- Added licensing info for audio files used in the Scipy notebook
- Deleted some clutter (an old attlist file which is superceded, and the extra-exercises which were a bit of a holding area and aren't really part of the course)
I have mirrored these commits in the sol branch.