This removes the assumption that an xeyes instance displays just a pair
of eyes, and instead allows future developers to implement different
kinds of ocular layouts.

Currently, the ocular layout system only allows for specifying offsets,
but a future change might also make different parts of the eye geometry
configurable: size of different elements, padding, etc.

Signed-off-by: Serge Bazanski <q3k@q3k.org>