Add bounding boxes to indices for flatbuffer images

[jarkenau]

Here:

seerep/seerep-hdf5/seerep-hdf5-core/src/hdf5-core-image.cpp

Lines 43 to 49 in 8d9cce7

	// set bounding box for images to 0. assume no spatial extent
	data.boundingbox.min_corner().set<0>(0);
	data.boundingbox.min_corner().set<1>(0);
	data.boundingbox.min_corner().set<2>(0);
	data.boundingbox.max_corner().set<0>(0);
	data.boundingbox.max_corner().set<1>(0);
	data.boundingbox.max_corner().set<2>(0);

[Mark-Niemeyer]

use #146 for that