Merge branch 'kt-mb/modified-LM' of github.com:JuliaManifolds/Manopt.jl into kt-mb/modified-LM

# Conflicts:
#	Changelog.md
#	docs/src/notation.md

Author: kellertuer

Changelog.md

@@ -29,6 +29,7 @@ We also unified a few of the internal solver state constructors.
 * the keyword `initial_jacobian_f` within `LevenbergMarquardt` is unified in naming to the residual values vector and called `initial_jacobian_matrices`. If you call `LevenbergMarquardt` with a single vector component, also a single matrix is allowed. (#617)
 * an internal field of the solver state of Levenberg-Marqwuardt was called `jacobian_f` the same as the functions whose result it meant to cache if applicable. To distinguish both, the field is now called `jacobian_matrices`. (#617)
 * the `max_stepsize(M)` on the [`SymmetricPositiveDefinite`](https://juliamanifolds.github.io/Manifolds.jl/stable/manifolds/symmetricpositivedefinite/) manifold was changed from returning `Inf`, which is the mathematical maximal stepsize to returning the square root of the maximum (floating point) value to avoid numerical instabilities.
+* title of "How to define the cost in the embedding" tutorial (#615)
 
 ### Fixed