collect: fix crash in case of non-valid utf8 database entries

g_markup_escape_text() does not tolerate invalid utf8 strings.
we need to to fix those upfront.
Italian translation updated
imageio: hard block extentions handled by rawspeed again

most if not all cameras should work now, the only exception
being missing panasonic aspect ratio's, which should be easy
enough to quickly add.
imageio: _blacklisted_ext now protects libraw from xtrans rafs
Merge pull request #633 from bartokk/master

Italian translation updated
update pt_BR master
Merge pull request #635 from guitorri/master

update pt_BR master
Try to add sane defaults to an empty XDG_DATA_DIRS
Merge pull request #632 from upegelow/collect_utf8_fix

collect: fix crash in case of non-valid utf8 database entries
Fix help message for picasa module

What the user needs to copy is the code given in the page, not the URL