Remove the "check for updates" and "Update ROM database" menu entries,
as well as the automatic update checking and all supporting code.

This fixes the issue with the emulator hanging without access to the
internet.

Updating code will be reimplemented in the future using something like
Sparkle. wxHTTP does not support redirects or https so is pretty much
useless now.

Also update the About box to bump copyright year to 2017 and change my
name to "rkitover", which is what I use on github, and mention other
contributors.