Add step buttons to animation controls.

[jterstriep]

Add "fast-forward" and "rewind" button to the bottom of map view. This would allow for an easier way to click through frame by frame. Right now, you have to enter a number in the date(year), then click tab or enter to actually go to the next frame.

[jterstriep]

Sorry, I didn't mean to mark this as a to-do for release. But it's nice to have if it is easy.