Add and fix few messages in second plural form for pl, be, ru languages

Add and fix few messages in second plural form for pl, be, ru languages

Fixed missed "singular" message which had word "one" instead of "{count}" for uk and ru because it should be used not only for "1" but also for "21, 31, ...".

Add formula for 2/3 form for Russian (Plural-Forms:...)
and Belarusian and Ukrainian formulas normalized to be the same for all three languages