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. 
I am not sure Mosek is installed on Travis server, so I add this macro USE_MOSEK. But I tested on my computer with ```./shogun-unit-test --gtest_filter=PrimalMosek*``` (also checked valgrind)
```
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from PrimalMosekSOSVM
[ RUN      ] PrimalMosekSOSVM.mosek_check_w_bounds
[       OK ] PrimalMosekSOSVM.mosek_check_w_bounds (50 ms)
[----------] 1 test from PrimalMosekSOSVM (50 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (51 ms total)
[  PASSED  ] 1 test.
```