czech (cs) translation, initial

[zvolsky]

Just a new language (cs) translation.

It is a little unsure if cs_CZ or cs should be used, but czech language is used in Czech Rep. only (except of really ultra small minorities in Romania, Serbia (or maybe Swiss or USA)). So cs is I think the proper way to go. And it is compatible with Django and Django Admin - this is probably the 1st point.

Best regards. Mirek Zvolský