animate double clicks

Rather than jumping from one camera center to another, the
camera slowly transitions between the previous and the current
center. This makes it much easier to track objects by eye.
add rnums to selection language
add Viewer.setCamera to set zoom/rotation and center at once
add rock and roll mode for viewer
remove unused code from gl-matrix

Shaves off a few bytes in total code size.
switch data order for remark 350 matrices
use auto-zoom after loading structure from pdb.org