Update copyright description

[fktn-k]

In this PR, I have changed the copyright since its content varies from place to place and that's confusing.

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Pull Request Checklist

Read the CONTRIBUTING.md file for detailed information.

• [x] Changes are described in the pull request or in a referenced issue.
• [x] The test suite compiles and runs without any error.
• [x] The code coverage on your branch is 100%.
• [x] The documentation is updated if you added/changed a feature.

Please don't

• The C++11 support varies between different compilers and versions. Please note the list of supported compilers. Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support. Please refrain from proposing changes that work around these compiler's limitations with #ifdefs or other means.
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[coveralls]

coverage: 100.0%. remained the same when pulling 1131d39bf61593018d647a20f42eac349b491abf on feature/update_copyright into 079bff121736de96daaa31eb605049f1659ce9d3 on develop.