Fides

* adds additional option value type validation
* fixes runtime warning for unbounded problems
* fixes optimization based stepback mode `refined`

* Fixes a bug in tracking that incorrectly indicated non-updating in hessian approximation
* Fixes a bug where curvature condition in BFGS approximation was not ignored even when corresponding option was enabled
* Fix subspace normalization for cases when newton step was within trust region radius
* Extend tracing by condition numbers

* Add option to track history of optimization for detailed debugging
* Add options to customize BFGS (and derived) approximation schemes by ignoring curvature condition
* Add novel hybrid method that switches approximations based on fraction of steps with inconclusive trust region ratio
* Remove option to include scaled gradient as candidate step
* Refactor step refinement and restrict it to subspace of base step
* Reduce logging output verbosity

* simplify and fix structured secant method based hybrid schemes
* removes the PSB approximation scheme

* Add `citation.cff` file
* update description
* bugfixes for hybrid hessian approximation schemes

* fix and better checks for Hessians with NaN values
* add citation information