Russian translation

Added russian translation to the modification. Both UTF-8 and ANSI encodings present. Added into existing structure. Maybe it would be reasonable to move language strings to a separate files while implementing multilingual support.

Known issue: if no file $languagedir/Modifications.russian.php exists there would be an error. 
Possible scenario: installation when no other mods are installed. 
Possible solution: add 'create $languagedir/Modifications.russian.php' if not exists.