Add ability to define project extents

Came up during Yaquina training. If large charts are loaded and you hit zoom extents in shell or survey it zooms out to the entire chart and it can be very annoying to have to zoom back in. It would be nice to have the ability to define the project extents and when zoom extents is selected it will only zoom to the defined area. Would be easy to make the selection by draging a box or using a boarder file.