Removing Regression

[ncborcherding]

Breaking Changes

• Removed regression task support across the package. The previous regression
  implementation was unreliable and is being redesigned. bHIVE(),
  honeycombHIVE(), swarmbHIVE(), refineB(), AINet, GerminalCenter,
  bHIVEmodel, honeycombHIVEmodel, and visualizeHIVE() no longer accept
  task = "regression" or numeric y.
• Removed regression-only loss functions (mse, huber, poisson) and
  regression metrics (rmse, mae, r2) from swarmbHIVE().
• Removed refineHuberDelta parameter from honeycombHIVE() and
  honeycombHIVEmodel.
• final_assignment_cpp() no longer accepts antibody_values or
  overall_mean arguments.