Update strings.xml

(RU) Various improvements and fixes. The some terms are unified with desktop clients (e. g. Sylpheed).
Change wording in changelog; fix typos
Use address object as contact picture instead of email address only.

Fixes assignment problems for emails sent by some issue tracking
systems, which send out mails with a fixed mail address on behalf of
different people.
Updated Slovak translation
Merge pull request #391 from pylerSM/patch-2

Updated Slovak translation
Merge pull request #390 from bboa/master

Update strings.xml
Don't performSend() on onSave().
Translated to Lithuanian