Make genotp more clearly state that the password can be used once but
allows permanent access (sorry for not making this clear earlier.) Use a
slightly longer password, and allow uppercase characters except for some
that could be ambiguous

Prevent labels from having .., /, *, control characters, or quotes (this
generally messes things up) and limit them to a reasonable length. We
might possibly also want to do this in snmp.lua, I'm not sure if that
will break things though

Previously on large server(s), there was an issue where because
chunkloaded computers all started up at once, so they all had the same
discovery message sending timer. This prevents that by starting each off
with a random offset. Also increases the interval for sending messages
from 15 s to 30 s, so that messages (which are the same, a lot of the
time) get sent less often.