Drop searching playbooks in /usr/local/share/debops.

We decided on IRC today, that we assume debops is used from a user
account so installing playbooks globally is not the common case.
Drop Makefile.

There is nothing useful here anymore: Scripts are now installed using
pip resp. setup.py, playbooks are no longer searched in
/usr/local/share/debops, so do not (un-)install them there.
Uninstalling scripts is done via pip.
Update Readme file to show installation using pip.
Some editorial changes to Readme.
Remove unused code.
Ensure all files have correct GPLv3+ header, copyright- and licence-note.
Move short description in scripts into pythonic doc-string.
Make `debops-default` use `view` again.

I changed this to `less` while testing, but `view` supports
syntax highlight for yml.
Update CHANGELOG.