pot/po update (update nb). translators plz look in wiki for how to check accels and other stuff before supplying your transl

using comments and Q_() for make disctioning of None and Unknown strings. this breaks strings freeze but I hope it is for the good and I hope it is the last time [sorry ppl]

typos and cleaner strings in atk strings that dkirov has added; pot/po update (some fuzzing sorry..)

using plural forms in a place where duganov reported, all devs, patchers have a look; also updating pot/po to match plural forms usage and some new strings changes from greek po [as I go on]; we now also have make gajim.pot to produce the pot with the help of intltool

I updated partially greek gajim.po and fixed some strings so I commit po and pot. there is a lot of job to be done before all strings are reviewed and become better