Show system message for OMEMO status in the conversation

[ghost]

Fix issue #125

[ghost]

Result of this PR: when user open a window for IM conversation:

• If OMEMO enabled, there will be a system message "OMEMO encrypt conversation: Enabled"
• If OMEMO available, there will have a system message "OMEMO encrypt conversation: Available"

[gkdr]

Thanks, I'll have a look. I'd probably rather add it as an option in the new options dialog though.

[ghost]

I saw the new options interface in dev. I could help to add this as a option if I have time to work on it.

[gkdr]

I was going to suggest adding it to the preferences.

[ghost]

The github has problem, I can not push to my forked repository. I can not do any operation to it. I tried to deleted the fork , but it is still appeared in my profile and could be visited. It looks like turned to a "read-only" status. I will try to wait for somebody fix it, and probably create a new pull request for this feature after it recoverd.