[Refactoring] redundant Levenberg Marquardt implemenations

**Is your feature request related to a problem? Please describe.**
The developer branch is now (5c1d95aa062bb14a9947cdffdd53f7d90a0f8e5a) containing a levenberg marquardt variant that supports box constrains and an classic implementation.

**Describe the solution you'd like**
Refactor the code yielding a single implementation that can be run constrained and unconstrained.