Migrating from uk.ac.ucl.casa.* to com.reades.* and bug-fixes

For simplicity's sake have migrated java classes to my own domain, and
am rolling out a number of significant fixes/changes:

1. Primitive support for GPX files.
2. MapThing is now smart enough to skip holes in Polygons.
3. Explicit support for TSV (tab-separated value) files.
4. Ability to reverse the order of points in a line or polygon (works
with arrowheads).
5. Arrowheads will come soon once I've migrated the code from the
Processing sketch.