Repo Management: Adds repo management templates

[AmirAbrams]

What is the purpose of this pull request (PR)?

Adds git repo management templates for pull requests, issues and contributing to the source.

Any background context to help the reviewer?

These templates are Github specific and some are relatively new. Github first implemented the PR and issue templates in February 2016. The contributing template was added in ~2012. Please let me know if you want me to change the verbiage in any of the templates. From my experience, these templates are helpful tools for the repo maintainer and the contributors. The contributing template verbiage was forked from Bitcoin

Was this PR tested and how?

Yes, on my forked repo and this uses the new pull request template.

Does this PR resolve an open issue (reference issue #)?

No.

More Questions:

• Does the knowledge base or documentation need an update? No.
• Does this PR add or change dependencies? No.