Rewrite PVector pretty much from scratch.

This unfortunately means replicating a bunch of code from PVector.java, but I can't
see a way around it.

Fixes https://github.com/jdf/Processing.py-Bugs/issues/67.

assert isinstance(PVector(1,2), PVector)
Permit 0-arg PVector() constructor.
Build 0359.
Tell PApplet where the proper sketch home is when running an unsaved, modified sketch.

Fixes https://github.com/jdf/Processing.py-Bugs/issues/65, and has the excellent bonus
effect of not copying enormous data files on modified, unsaved sketches.
Fix unit tests and static sketches to know where their sketch homes are.
Build 0360.
Fix a dev-mode bug that caused the debug sketch service to double-launch the runner.
Friendlier error messages for certain classes of syntax errors, especially java-style colors like #FF33AA.

Fixes https://github.com/jdf/Processing.py-Bugs/issues/71.
Build 0361.
Expose Table.
Fix https://github.com/jdf/Processing.py-Bugs/issues/68
Build 0362.