add cc/bcc toggle and hidden cc/bcc fields, also Reply all and Forward back again

Working on cc/bcc as per https://github.com/owncloud/mail/issues/96

* [x] Introduce the fields for to and cc in replies as well. (Optional though, not as present)

@DeepDiver1975 
Add the "..." to l10n. Are you sure it has the same meaning in every language?