[Openstreetmap] More Landsat stuff

[Nick Whitelegg]

Hello everyone,

Have now improved the Landsat support in osmeditor. The app is now more robust 
to moving around with the arrow keys and scaling - if you scale a new load of 
Landsat data at the new scale will be grabbed. Get it from the OpenStreetmap 
subversion archive or at 
http://www.free-map.org.uk/downloads/osm-editor-080505-2233.tar.gz.

I have also now added polygon drawing support. Polygon mode (the fourth mode 
toolbar button) allows you to hand-draw polygons (woods, lakes etc) over the 
top of such features identified through the Landsat data. Polygons can be 
saved to GPX: they will be defined by the <polygon> and <polypt> tag within 
the <extensions> tag. The rationale for putting them in GPX rather than some 
other separate file is that I wanted to keep one map "scene" (paths, 
waypoints and polygons) all in the one file.

Nick