Apply general writing codestyle for GitHub Pull Requests:
- move the "Closes #" text down to its own line, as GitHub prefers to read the git command without preceding text.
- move the text "(Does it build, tested in-game, etc.)" down to a new line to indicate where we want the info inserted.
* pull_request_template.md improvements
- hide bottom comments from saved view on github.com
- add 1 empty comment line for some sections (suggest where to write)
- add tick boxes for the branch names
- "TODO" -> ToDo (from the 2 words "to do")
* Update pull_request_template.md
