* glom/libglom/data_structure/field.cc: to_file_format():
	The Value might have a GdaBlob that needs to be read first, to get the
	GdaBinary. This can happen with SQLite.
	* glom/libglom/python_embed/pygdavalue_conversions.cc:
	glom_pygda_value_as_boost_pyobject(): Handle GdaBlob too, though neither
	this or the GdaBinary case use the data length, so this code is doomed
	if it is ever used. I need to find out if Python can really represent
	binary data, or if this should just not be handled here.
	* glom/utility_widgets/imageglom.cc: get_binary(): Handle GdaBlob
	too in the original data.
	* tests/test_selfhosting_new_then_image.cc: Handle GdaBlob in the
	data that is read back, for SQLite. Uncomment the SQLite test, fixing
	make check with the latest libgda.