change in date format in 2.7

[Alen Siljak]

   To get back to Sebastien's question: this does seem like a breaking
   change at this stage. Going back to 2.6.19 with the database where a
   few transactions have been entered in 2.7.2 shows the dates as
   1970-01-01.

   >Alen,
   >
   >Oh yeah, SQLite3. That doesn’t have a date type so the backend stores
   a formatted string. We use >ISO formatted date output for a lot of
   other things and I didn’t see a good reason to write a >special output
   function just for the SQLite3 backend when I rewrote the SQL backend in
   C++.
   >
   >We consider the data file formats and SQL schemas to be private
   implementation details.  If we make >a change that breaks Piecash, too
   bad. I told Sébastien that repeatedly and at length three years >ago
   when he embarked on the project.