Fixes #34, maprect(n) is the default
Fixes #34, maprect(n) is the default

Now when a mapcanvas(n) object is created, it uses a geo-references by
default. The default map background hasn't changed, it's still a
1000x1000 canvas, but it has 42 lat, 45 lon at the upper right corner
and 38 lat, 51 lon as the lower right corner. This corresponds to an
area near the Caspian Sea.

AthenaModel/mars,AthenaModel/mars,AthenaModel/mars,AthenaModel/mars