Two new debug features (See Description)

Added the `options.image_mode` and `options.pause_mode` debug options
to ample.
* `options.image_mode` causes the state information to be displayed in
image format instead of a 1d plot when `options.debug = 1`.
* `options.pause_mode` will pause ample after each iteration and wait
for a key-press before continuing. This is useful when `options.debug =
1` so that one can view the current state information.