Examples need to be distributed in package

The example scripts are maintained in trunk but aren't (yet) distributed in packages of the code, or installed on user systems.

First, we need to stop tracking massive data files - they'd make the package too big and they're not especially useful in their own right. The useful output data is already contained in the plot files so that's enough. There's maybe some benefit in keeping small data files (e.g., tables of energies of subband minima).

We can then distribute them using EXTRA_DIST in Makefile.am so that they end up in the /usr/share (or similar) folder on the user's system.