Starting to sketch out building and cleaning.

Also nixed some old cruft.
Use URI not URL.

URL is bad bad bad.
Source and bin dirs no longer customizable.

I'm making the rules here, and I decree that you can put your damned source
files where I want them and I'll put the built class files where I want them.
Wired up building Java code.

Scala coming next.
No longer use srcdir and bindir.