Harris Hawks Optimization integration

[sisco0]

Summary

The Harris Hawks Optimization Algorithm has been integrated into NiaPy.

This algorithm goes on the line of Nature inspired optimization algorithms.

Having completeness and state-of-the-art as a goal for the NiaPy project, this
algorithm has been added, as it has been recently published (2019) in a JCR journal.

Unitary tests for the algorithm has been added as well.

Other Information

As this is my first algorithm integration development, please take care at its review.
I would be happy to fix the issues found at it as well.

I used BatAlgorithm as a template for writing this script.

Even more, I added some useful comments for other source files as well.

Please feel yourself free for modifying these.

I want to thank Iztok, Jr. for guiding me through this development.

[todo]

Fix bech by bench

NiaPy/NiaPy/tests/test_algorithm.py

Lines 300 to 303 in defecd5

	# TODO Fix bech by bench
	task1, task2 = TestingTask(D=D, nFES=self.nFES if nFES is None else nFES, nGEN=self.nGEN if nGEN is None else nGEN, benchmark=bech), TestingTask(D=D, nFES=self.nFES if nFES is None else nFES, nGEN=self.nGEN if nGEN is None else nGEN, benchmark=bech)
	return task1, task2

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This comment was generated by todo based on a TODO comment in defecd5 in #280. cc @sisco0.

[todo]

Add one-liner np.clip approach

NiaPy/NiaPy/util/utility.py

Lines 48 to 52 in defecd5

	# TODO: Add one-liner np.clip approach
	ir = where(x < Lower)
	x[ir] = Lower[ir]
	ir = where(x > Upper)

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This comment was generated by todo based on a TODO comment in defecd5 in #280. cc @sisco0.

[sisco0]

Please, review tests performed, as reproduction errors are thrown because of random number generator.
This happens not only at this algorithm, but for others as well.

[sisco0]

Accepted at my fork the changes proposed by @firefly-cpp .

[sisco0]

Reproduction tests errors were fixed successfully.

[sisco0]

I added some fixes for flake8 styling over hho.py file so it goes well with it.