Disable OTR chat logging by default

dramb-lys

OTR stands for "Off-The-Record", and by design supports perfect forward secrecy. Logging negates this. Chelsea Manning was prosecuted using alleged OTR chat logs.

TingPing

Should be doable to spam `/chanopt` disabling _text_logging_ and _text_scrollback_ any time an OTR chat is started, ideally setting it back to previous state when finished (which is a bit tricky).