Implement LP solver using qpOases. Implement a more efficient primal...

Implement LP solver using qpOases. Implement a more efficient primal formulation of the LP to compute robustness of a given CoM position (LP2 in the code). Even this formulation sometimes gives wrong results with coin-or solver, but not with qpOases. Implement first performance tests: qpOases seems faster than coin-or solver and fastest formulation seems to be the dual LP (about 0.1 ms for 32 generators). PP algorithm is instead very slow, much slower than in Steve's code, but it's not clear why.