Implement private messaging

[themiron]

Implement simple private messaging support:

1. { ircChan: 'bot', tgGroup: 'tg_username' }
   IRC contact->bot messages will be forwarded to TG as tg_bot->tg_username.
   Replies to that messages will be forwarded back to IRC contact, IRC name prefixing should be enabled.

2. { ircChan: 'contact', tgGroup: 'tg_group' }
   IRC contact->bot messages will be forwarded to TG as tg_bot->tg_group.
   Messages from tg_group will be forwarded back to IRC contact.

[Bysmyyr]

looks good but fix the checks please :)

[themiron]

sure, thanks for the remind

[themiron]

@Bysmyyr have fixed my changes, but checks are still failed due unrelated pre-existing code

[themiron]

any news?

[FruitieX]

Thanks! Sorry for not responding earlier, I'm a little bit inactive here as of lately. :)

[themiron]

thanks!