renamed the `draw` kwarg to `plot`

- `draw` still exists as an alias for nodebox scripts
fixed transform inheritance for non-drawn grobs

- they were peeking at the internal variable rather than letting the
property handle inheriting from the context
plot() and bezier() updates

- plotstyle() is dead, long live `with plot(True|False)` for
controlling auto-drawing of primitives
- the `plot` kwarg in individual calls to primitives overrides the
global setting
- the plot(grob) usage now defaults to drawing a copy. pass live=True
if you want the reference to point to the on-canvas object.
- `with bezier` now accumulates primitives as well as the *to commands
- arcto() can be used cg-style when called with a dest point & radius
(the simplified invocation could use a rethink)