Update strings.xml

Updated Polish translation (based on English version of strings.xml). Particularly, 'status_closeout_warning' was included
Update strings_not_translatable.xml

After 6 months of supporting Polish translation I added myself to the list :)
Update strings.xml

two bugs corrected
Merge pull request #3029 from mieczyslaw/master

Update to Polish translation and I added myself to contributors :)