CMosek added variable bounds

Hey @iglesias I made changes in Mosek.cpp for adding bounds on variables. Unfortunately, I have to touch many files to make the arguments consistent. Could you review the little patch for me? 

I am not sure we want to add unit-test for Mosek related class. But I am pretty sure these changes make sense. I have tested them on my own computer. BTW, I think @Jiaolong will test this part of code in his GraphCut inference thoroughly. 
Sorry, I should explain this. 

Look at Mosek.cpp:84-89: https://github.com/shogun-toolbox/shogun/blob/develop/src/shogun/structure/PrimalMosekSOSVM.cpp#L84
lb and ub are supposed to set up in init_primal_obj() and then input to Mosek solver at mosek->init_sosvm(). 
This is why we'd like to use reference for lb and ub, as exactly the same as the regularization matrix C.