Add convenient way to post the MultiMC log

[peterix]

Ideally, anonymized.

[spannerman79]

Perhaps using https://gist.github.com/ ?

[Kilobyte22]

We already use paste.ee for Minecraft logs, so I'd suggest also using that for MultiMC logs.

[Arzte]

yeah, might be easier to use the same thing for pastes

[peterix]

Anyway, duplicate of GH-649