Fixing indexes, random typos in thesis.
Remark the use and the semantics of the yield statement in Dixon.
Again on off-by-one errors.
Add bland check for the primes database file to exist.

This shitty primes file thing must be substituted asap with a truly accessible file.
Merge branch 'master' into dev/mpi
Creating run_question().

Yet another interface for handling questions, to be used both at runtime and
while testing.