Cardboardlint

- Improve interaction with Roberto.
- Hide duplicate messages.

- More verbose output. List of selected files for linting is always shown.
- Fix default location for Python command-line scripts is ./bin, not ./scripts.
- Wall time of linters is printed.
- Few cleanups.

- Added support for fixers. The following liners can also fix problems: header, whitespace, autopep8, yapf, black. The latter three are new.
- Removed some Python-2 compatibility code.
- Replace nosetests by pytest.
- Add more context to README.
- Add RST linter.

Add option for number of processors to use.

Add missing config options for cpplint.

First release, mainly in anticipation of API-breaking changes, which will result in a major version increase. By making a release, we can handle this change in API gracefully. Notable features include:

- Support for the following linters: cppcheck, ccplint, doxygen, flake8, header (internal), import (internal), namespace (internal), pycodestyle, pydocstyle, pylint, whitespace (internal), yamllint

- For all supported linters, the output can be restricted to files and (lines in those files) that have changed between two git commits. In pull requests, this will then only show errors that are relevant for the code touched in the PR. This is intended for making life easy for contributors, i.e. to not bother them with linting issues in code they have not touched.

- Flexible file filtering, essentially a simplified version of rsync's file filtering rules.

- Consistent and colored output for all linters, making it easy to process linting issues.