Option to use same OTR key for new new accounts

[varac]

When my nickname is taken, and I get a new alias assinged by irssi (i.e. varac_) a new OTR key is generated. Please include an option to use the same existing key for new accounts. This would simplify fingerprint verification in the sense that my peers don't have to verify yet another FP when chatting with an alias of me.