Naming of `OptimizerMethod` subtypes.

[benedict-96]

Sub types of OptimizerMethod shouldn't be called AdamOptimizer, MomentumOptimizer etc.
Adam, Momentum (or possibly AdamMethod, MomentumMethod) would be better!

[michakraus]

Solved. The methods are GeometricOptimizers' GradientMethod, MomentumMethod and Adam, which GeometricMachineLearning re-exports. The old names remain only as aliases (src/GeometricMachineLearning.jl), and the 0.9 plan deletes them.