Update logging library to pull in progress meter
Improve performance of neighbourhood computation.

To this end I implemented a custom algorithm for computing neighbourhood,
instead of relying on a boost::bfs with early termination. This increases
performance by at least two orders of magnitude.
Fix unittests of degree computation.
Add progress meter to Kelly-width computation
Improve performance of treewidth computation (esp. minor-min-width).

Here I used some information that we have to save on the number of
increase and decrease operations in the Fibonacci heap. These operations
currently require most time. Improves performance by roughly one order
of magnitude.

In the process I added a progress meter to get a sense of the speed of the
computation.