[Snails] Just return the address in FromPair().
[Snails] Prefer range-based for to std::for_each.
[Snails] Refactored addresses getting to a function.
[Snails] Pass shared_ptr's in ComposeMessageTab by const ref.
[Snails] Set CC and BCC.
[Snails] ToMessageIdSequence().
[Snails] Use const refs where needed.
[Snails] Set InReplyTo and References headers on send.
[Snails] Store message being replied to.
[Snails] Set references for the reply being composed.