Convert the bug report and feature request templates to GitHub issue forms.
Rewrite the pull request template to require that non-trivial changes are
discussed in an issue first, and to spell out that backend changes need a
clean test_all run and a test account for the integration tester before
they can be merged. Document the latter requirement in CONTRIBUTING.md.
Remove the legacy ISSUE_TEMPLATE.md which is superseded by the forms.
Nick Craig-Wood
3732e010e2