Support creating GitHub issues with an issue template

When creating new issues in GitHub, an "issue template" can be applied. It's not possible today to specify an issue template when sending an Aha! record to be created as a new issue in GitHub. This is problematic if we also need to send the record description to the "Body: Data" field in GitHub, and if the Body is empty, as the "Body: Data" field cannot be updated when the Body is empty. By selecting an issue template, we can insure that the Body is never empty.