List upload size limit on /about page

The upload size limit, which is in nodeinfo, should be converted to human-readable form and listed on the /about page.

Mockup:

I was going to open a similar issue, it would be nice to show all limits actually (avatar, bio length, etc.), so that users know what to expect, instead of getting an upload silently refused and no way for them to know the limits.

added easy ticket label

mentioned in merge request !1308 (merged)

closed with merge request !1308 (merged)

mentioned in commit bdb994d4