Add unit tests for NLOpt

src/classification/ConvexHull1D.hpp

src/feature_creation/node/operator_nodes/OperatorNode.hpp

...lowed_operator_nodes/abs/parameterized_absolute_value.hpp

...ator_nodes/abs_diff/parameterized_absolute_difference.hpp

...or_nodes/allowed_operator_nodes/add/parameterized_add.hpp

...or_nodes/allowed_operator_nodes/cb/parameterized_cube.hpp

...s/allowed_operator_nodes/cbrt/parameterized_cube_root.hpp

...or_nodes/allowed_operator_nodes/cos/parameterized_cos.hpp

...nodes/allowed_operator_nodes/div/parameterized_divide.hpp

.../allowed_operator_nodes/exp/parameterized_exponential.hpp

...odes/allowed_operator_nodes/inv/parameterized_inverse.hpp

...or_nodes/allowed_operator_nodes/log/parameterized_log.hpp

...es/allowed_operator_nodes/mult/parameterized_multiply.hpp

...ator_nodes/neg_exp/parameterized_negative_exponential.hpp

...or_nodes/allowed_operator_nodes/sin/parameterized_sin.hpp

...owed_operator_nodes/six_pow/parameterized_sixth_power.hpp

..._nodes/allowed_operator_nodes/sq/parameterized_square.hpp

...allowed_operator_nodes/sqrt/parameterized_square_root.hpp

...des/allowed_operator_nodes/sub/parameterized_subtract.hpp

src/inputs/InputParser.hpp