Refactor map state & fix extent issue

Trying to simplify map state and updating map state:

• Flatten out map state structure so that: extents, leafletmap, and exists are all at the highest leve. There is no mapViewport nested inside of map state anymore.
• Previously there were two separate actions to update extents in state: mapViewportChanged and mapViewportExtentChanged, now there is just one mapExtentChanged
• Updated names on facades, actions, selectors, and state for more consistency.

Also, fixed a bug where the map was using the center/zoom combination when rendering the map. Now there is no center/zoom and bounds are set immediately after instantiating the map.