Bring Pytave into core

[Jordi Gutiérrez Hermoso]

I have a wild idea. I like Python, and I think Numpy and Scipy are a
great tool. Interfacing Scipy with Octave is also a good thing.

There is oct2py that interfaces between Python and Octave, but I am
not happy with its overall pipe-based approach. Instead, I think
Pytave is doing the right thing by directly calling the Octave C++
API, but this has two disadvantages: it's difficult to build and
install, and it has gone unmaintained, so it no longer adheres to the
current API.

I therefore propose to bring Pytave into Octave proper. This would
make Numpy an optional compile-time dependency of Octave, sort of like
Java, but it would potentially mean that anyone who installs Octave
can now do "import pytave" from Python and have two-way in-memory
communication with an Octave process.

Naturally, this would not be for the 4.0 release, but the one after
that.

Thoughts?

- Jordi G. H.