ast: No need for convex hulls to be smoothed

By their nature, convex hulls have a sort of "built-in" smoothing anyway.
smurf: JSA tiles now use a convex hull to outline the good data.

A convex hull is the shortest polygon enclosing the good data amd so it
may enclose some bad values too. A convex hull is better for acsis data,
which can include multiple blobs of contiguous good data values.
ast: Fix bug with very short lines on the sky
ast: Add new attribute SimpVertices to control simplification of Polygons
kaplibs: Do not specifiy uncertainty in convex hull

The recent changes to AST regarding simplification of Polygons means that
it is no longer necessary to specify an uncertainty in the outline
polygon. Previously, bending of the polygon edges caused by the
non-linear mapping from pixel coords to sky coords caused the
simplification of the Polygon to fail, and so prevent it being converted
to STC-S format.