Matchingproblems

Couple of bug fixes.

- Fixes bug in lecturer load balancing model setup.
- Matching size output.
- Fixes broken link in README.

Adds optimisation -mincostlsb which minimises student costs and lecturer load vs target differences. Includes student and lecturer multipliers.

Also adds ability to stop greedy and generous optimisations at a given rank.

Adds student and lecturer multipliers for min cost and min squared cost optimisations.

Also updates dependency versions and fixes a few bugs.

Pip package requirements updates and minor readme update.