set the reason to null at unassign-method
adding reset-funciton to optimisation interface
adding the instance variable 'variables' to the interface
adapting the CDCLLike solver to the new interface
fixing a bug
adding an objective function
adding a test for the reset-method
implementing an optimisation by branch and bound
adding tests for branch and bound optimiser
fixing the same bug as in LinearOptimiser class
test the reset method of the optimiser
adding the underestimation procedure maximal independent set and adding an activity variable heuristic
fixing an copy and paste error