Remove `/moveto` command

[joesanford]

While originally well-intentioned, the /moveto #channel command seems to tend to stifle conversation instead of moving it to a better channel. IMO it should be removed, and people should just ask kindly for the conversation to move. As @mrasband put it, it's a bit cold.

[mattrasband]

Agreed on this, it tends to totally shut down the conversation rather than move it. If nothing else, we should consider alternatives. I think right now maybe /moveto could auto-generate a message from the current user and post as them instead (or just request people to nicely ask)? Something like:

Sorry to ask this, but it seems this conversation has gone off topic and is conflicting with ongoing on-topic conversations here. Can you please move to #<channel>