Instead of only checking for the validity of the impl class, the view
classes now also check if the view data is valid. This improves debugging in
cases (when the trying to access, for example, an AtomView whose EntityView has
been deleted.

This avoids the crash in BZDNG-193. Hopefully we will be able to reverse it,
once the trolltech guys fix the bug upstream.

For debugging purposes

fix race condition in PythonInterpreterWorker that shows up when two nested event loops trigger the Wake slot.

this seemingly simple change required a rather gross hack to avoid a crash when
the file type dialog is destroyed. Currently the FileTypeDialog is allocated on
the heap an leaks. This is not nice, but since the file type dialog is very
rarely used, this seems to be something we can live with for the moment. I've
opened ticket BZDNG-192 to track the issue.

We now grant low-level access to the energy calculation, but without
exposing the implementation details. These methods are all completely
reentrant and can thus be used in a multi-threaded environment.

The choice between old/extended format is done automatically by the
importer and exporter, the user doesn't have to take care about
selecting the correct format.

The extended writer automatically kicks in when the entity contains
more than 99999 atoms.

This is very useful when deploying a single program building
on the C++ libraries only.

clustalw with external options, including unittest; renumbering accepts seq and aln as input;unit tests