Various improvements to development infrastructure

[bouweandela]

Various improvements to development infrastructure

• Simplified setup.py/setup.cfg
• Mention nclcodestyle in CONTRIBUTING.md
• Mention codespell in CONTRIBUTING.md
• Enable more lintr linters
• Documentation on how to make a release
• Conda package files now located in the conda package directory
• Run more relevant tests on CircleCI
• Unpin matplotlib, tiledb, libblas
• Remove the dependency on mock by using unittest.mock from the standard library instead

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Tasks

• Create an issue to discuss what you are going to do, if you haven't done so already (and add the link at the bottom)
• Give this pull request a descriptive title that can be used as a one line summary in a changelog
• Circle/CI tests pass. Status can be seen below your pull request. If the tests are failing, click the link to find out why.
• Preferably Codacy code quality checks pass, however a few remaining hard to solve Codacy issues are still acceptable. Status can be seen below your pull request. If there is an error, click the link to find out why. If you suspect Codacy may be wrong, please ask by commenting.
• Please use yamllint to check that your YAML files do not contain mistakes

[bouweandela]

Note that the conda build is failing on CircleCI because it runs out of memory. When running it on a machine with more memory, it works just fine.