Create Octave package for release

Octave has its own package manager to control what extensions are installed in the system.

The following changes use the source in the matlab directory to create an Octave package. This should be preferred method to add libsvm to Octave as it allows the package to be loaded or unloaded, listed as installed package, etc.

In addition, it uses the code in Matlab to keep the duplicated code at minimum.

A few things would be very useful to simplify this script:
  * a CITATION file at the core of the repository with instructions in how to cite the library. Rather than parse the README file, I just copied the text and made the script generate it.
  * an easy to parse file with the version number as I had to parse it from the svm.h file.
  * some metadata file from which to generate the DESCRIPTION file

Still, has it is, running `./release_octave_pkg.py` will generate a `svm-3.17.tar.gz` file which can be installed in Octave with `pkg install svm-317.tar.gz` and then loaded or unloaded with `pkg load svm` and `pkg unload svm`.