Fix delete visible waypoints when map is scaled 2x

It used to delete over 4x too much area
Reorder map menu; add buttons to cycle through the maps quickly
Prevent drag starting on map cycling buttons
Bigger oversize on the map tile cache
Skip map redraws if the tile loader has got behind the UI activity
Add an on-screen button for toggling the 2x zoom feature
Add lat/lon display to waypoint editing screen
Fix handling of date line (partly)
Fix remaining issues with wrap at dateline and getting too near poles
Allow zoom out to level 2
Split functions out of Map into a derived class