License crawler for third party golang libraries

[Bobgy]

A set of CLI tools to automatically crawl license info for third party golang libraries.

Please first review CLI README for the overall workflow: https://github.com/kubeflow/pipelines/pull/2393/files#diff-d58ea8967fc24137b9d349dd2391e2b1

Also a trick is to filter out all csv and txt files when reviewing: https://github.com/kubeflow/pipelines/pull/2393/files?file-filters%5B%5D=.md&file-filters%5B%5D=.py&file-filters%5B%5D=dotfile it leaves only important stuff for review

File generation dependency graph is like:

    get-github-repo   get-github-license-info      concatenate-license
dep.txt =========>repo.txt =========> license_info.csv ======> license.txt
          //
with dep-repo-mapping.manual.csv

dep.txt: list of golang dependency names
repo.txt: list of github repos
license_info.csv: list of repo name, license html url, license name, license download url
license.txt: concatenated license file

/assign @Ark-kun
/cc @neuromage
/cc @IronPan

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This change is 

[Ark-kun]

/lgtm
@IronPan Can you please take a look?

[IronPan]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: IronPan

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[IronPan]

Thank you @Bobgy this is awesome.