update pl.po
Merge pull request #333 from nalesnikld/master

update pl.po
removed obsolete strings
.po files updated
fix de.po
translate new strings in ru.po
delete not used html tags
Merge pull request #329 from X-NicON/mfix

Update de and ru .po
Fix library explorer action in linux.
removed the ampersand, where this is not "ASCII" character
Replaced method call "confirm window". Now button be translated