Memoize evaluation results across multiple processes about hyperactive

[SimonBlanke]

I managed to implement the shared memory dictionary for multiprocessing in 5439daf. It requires >=0.3.3 of Gradient-Free-Optimizers (because I needed to enable the pass through of the shared memory dict).
The shared memory dictionary is automatically activated if memory=True and is shared between all objective functions that are equal. There is no additional input required by the user. Compatibility with the memory_warm_start parameter is also ensured.

The shared memory is tested with multiple tests that confirm the speedup for n_jobs>1.

Offtopic @0liu: The early stopping also works for Hyperactive v3.3.0

This feature was a great idea! Thank you @0liu for suggesting it.

[SimonBlanke]

Hello @0liu,

this is a great suggestion! I did some reading about this topic and I think it should not be that difficult to implement (but maybe I am wrong with that ;-) ).
I will do some testing/prototyping for this feature in the next few days. I'll get back to you when I have an update.