Original code failed when 'limit' key is set to None.

http://bugs.jquery.com/attachment/ticket/5968/0001-Fix-jQuery.ajax-success-function-being-called-when-H.patch

When importing back ace.js containing a last line with whitespaces only, the
last line was not imported, and thus the file could never been downloaded
completely as its really size was less than the one on the File ZODB object.

Counting all documents matching some criterion has a cost proportional to
the number of those documents. Modules grow large easily (the effect
becomes quite noticeable from ~50k), and this information costs too much.

Provide compatibility with non-upgraded products.
Also, update erp5_l10n_fr translation.

Allows telling user whether what he sees is the whole result set, or just
a limited sample of it.

because they are mostly used in non-web mode.

This is also fixes the case where an old version of ERP5Site_reindexAll is used,
when erp5_core is not the first BT being updated.

If PATH environment variable is not defined, this Products cannot be
imported. Followup of 399f95f9.

There are a lot of misses in this function because related keys must have
precedence over homonym columns, which makes it cost a *lot* of cpu time
to just return None.

Not perfect yet (what if definitions change during the same transaction ?),
but better than previous state.