do not default to check_for_new_version True until we have a pseudo thread doing that [or else in heavy net load Gajim takes a long time and user think we need to hugely optimize our code]

some more translatable strings, updating gajim.pot and greek gajim.po [100%]. I think it should be ok now but you never know

what glade tooltips calls size usually set to minimum is misleading and does not allow GTK+ to resize so longer strings [from translation] can be shown in the windows. So removing that so translation are readable [coz before this commit we were focusing on English or at the best French translation and were doing required sizes]. If someone wants to *propose* sizes that needs to be done in the default size area [first tab in Glade]. Translators enjoy

better strings [not more clear but TYPOS in English and unknown words] {so I had to break the string being frozen} {sorry for that}
also introducing greek transl [half tooltips remain with english text, but 0.7 can live with it if I do not get to finish it before 0.7]