added initial multimode topic branch modules
Added null mode for dummy activities
before adding the nonrenewable resources
adding the nonrenewable resources
added test for checking feasibility of solution to mrcpsp wit nonrenewable resources
Added naive implementation of multimode rcpsp evolutionary algorithm based solver (exact copy of single mode solver)
Removed duplicated code
Unified Multimode solver with single mode solver
Added goal function evaluation to multimode genetic algorithm formulation
Factored out common code in Problem class