Implement batch addition in archives

[btjanaka]

Description

The add() method will add solutions to the archive as a batch, which should greatly increase the archive speed.

add_single() is now the corresponding method which adds just one solution to the archive.

We obtained roughly 2x speedup on the sphere example -- python sphere.py cma_me_imp_mu and python sphere.py cma_me_imp took 60-65s (compare with 140s in #220 (comment)). Note that this is all without numba, i.e. batched operations without numba are faster than single operations with numba.

TODO

• Implement add_batch()
• Update docstrings
• Rename add() and add_batch() to insert() and insert_single() for consistency with the rest of the API, e.g. index_of() and index_of_single() No point since we would have to change AddStatus, and we will check array shapes anyway
• Rename add() and add_batch() to add_single() and add()
• Write tests
• Fix existing tests
• Fix add() in SlidingBoundariesArchive -> followup PR
• Check for regression on sphere example

Questions

Status

• I have read the guidelines in CONTRIBUTING.md.
• I have formatted my code using yapf
• I have tested my code by running pytest
• I have linted my code with pylint
• I have added a one-line description of my change to the changelog in HISTORY.md.
• This PR is ready to go

[btjanaka]

self-review

[itsdawei]

Good work!