Python package installation incorrectly installs data files

[rt121212121]

Reported by @SomberNight.

Python packaging supports two data inclusion mechanisms, package_data and data_files. Package data is data included inside the Python package, which for us is the top-level module electrumsv. Data files is where you want to install files, which may be inside the package, alongside it or somewhere nearby, in either an external location (/var, /etc, and so on) or relative to the installation directory.

Research results in claims that package_data and data_files are hard to get right, and it is enough and recommended to just ensure the data files are included in the MANIFEST.in file (which the graft electrumsv will do), and instead set include_package_data=True.

[rt121212121]

I can never seem to get the egg to include the data files, but the tgz and zip include them. However, since the eggs are deprecated, no more time will be spent on this.