Addition of new layers to lattice graphs, and fine control of bounding boxes

Layering in lattice Demonstrates the layering abilities of layer(), as.layer(), and related functions from the latticeExtra package. These abilities, due to Felix Andrews, add substantially to what is readily possible using functions in lattice. NB also the function segplot() that shows limits around the points in dotplots.
Control of bounding boxes Shows how to obtain L-shaped bounding boxes for panels, and to omit boxes around strip labels, as required by some journals. Also demonstrates detailed control of strip labels.