request backticks for logs

PR #2413 added an issue template, but just adding files to the project
directory upsets the packaging scripts: we need to explicitly include or
exclude them.

Move the template into a .github directory to make that easy, and to de-clutter
the root a bit.

Added instructions for checking server version.

Responding to review comments.

Removed the sentence encouraging people not to file a bug - if people are in doubt we'd rather they filed a bug than gave up entirely.

Oops capital L.

A new issue template proposed to try and steer people towards #matrix:matrix.org for support queries relating to running their own homeserver.