refactor filter

apply isNotFuzzy filter more early, less cycles spent in loop
refactor isTranslated filter

apply filter more early to save some cycles in the element loop
filter out obsolete items from catalog

such items should not be in any catalog. In the real world, such items
won’t have a module extracted by create_pot (that’t why those strings
have been marked obsolete). They would clutter up the log with warning
messages.