Allow control points to be optimized

[jvanvugt]

Adds an option to the Control_Point_Parameter struct to enable optimization of control points in BA, defaults to false so behavior is unchanged.

[pmoulon]

@jvanvugt thank you for the pull request.
Do you have any examples to share to show how much your control points changed during the process?

[jvanvugt]

In my use case, I'm detecting fiducial markers in images and adding them as control points after doing a regular reconstruction. They are triangulated with TriangulateNViewAlgebraic and then I run BA to minimize the geometric error. I'm not sure how much the points still move but it would be the difference between the algebraic and geometric error.