Update strings.xml

(RU) Various improvements and fixes. The some terms are unified with desktop clients (e. g. Sylpheed).
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().
Fix JavaDoc to match the changes in ContactPictureLoader
ContactPictureLoader code cleanup