* Update PULL_REQUEST_TEMPLATE.md
Removed a defunct hyperlink and placed an intuitive directive in its place.
* Updated PULL_REQUEST_TEMPLATE.md to include comment
* Updated PULL_REQUEST_TEMPLATE.md to include lts backporting
* Remove the description header. It is confusing because commit message body goes before it
* Explicitly require human-readable changelogs
* Explicitly require links to the external changelogs/diffs
* Introduce the pull-request template.
This change xplicitly sets expectations from pull requests.
Reason:
* Highlight the need in autotests and JIRA issues for bugfixes
* ask PR creators to propose the changelog entries for their changes.
* Provide hints about referencing people
* Move the pull request template to .github