Moved global OTR settings to [otr] group
Added /prefs otr
Added autocompletion for /account set <account> otr <policy>
Added OTR policy account preference
Moved OTR policy check to otr module
Override global OTR policy with account OTR policy
Added otr property to /account help
Added otr to /account clear properties
Merge branch 'master' into xep-0223