c++ implementation and bidings of the frame placement cost + unit-tests

Merged Carlos Mastalli requested to merge cmastall/crocoddyl:topic/cpp-cost-frame into cpp_devel

This PR tackles the issue #195 (closed). Additionally it includes unit-test of Python bindings for control and frame placements costs.

It also solves the issue with the Python unit-test in the cmake submodule.

Edited by Carlos Mastalli

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