ReplyTextField: Autocorrection enabled by default

Closes #2660
Closes #2531

@aerych may i bother you with a violent review?. Two issues, at the price of one Pull Request!

Thanks in advance!

Honestly, i opted for the `didSet` pattern because it just means... less lines of code (that's it!). You've got a valid point here: what if the local property gets out of sync with the UITextView storage?.

Since i've used this pattern, actually, all over (ReplyTextField, RichTextView, NoteBlock*TableViewCell), we should discuss this / add an issue to change it all in one shot!.