removed dim from linear variables

include/curves/curve_constraint.h

include/curves/helpers/effector_spline.h

include/curves/linear_variable.h

include/curves/optimization/definitions.h

include/curves/optimization/details.h

include/curves/optimization/integral_cost.h

include/curves/optimization/quadratic_problem.h

include/curves/quadratic_variable.h

python/curves_python.cpp

python/optimization_python.cpp

python/python_variables.h

python/test/optimization.py

python/test/sandbox/fit.py

python/test/test.py

tests/Main.cpp

tests/load_problem.h