- point to main Calamares site in the 'part of' headers instead
of to github (this is the "this file is part of Calamares"
opening line for most files).
- remove boilerplate from all source files, CMake modules and completions,
this is the 3-paragraph summary of the GPL-3.0-or-later, which has
a meaning entirely covered by the SPDX tag.
The TODO said it was unused: it **is** used, but only in
a very limited scope. Drop it from jobs where it wasn't
useful (e.g. those that just return prettyName(), outside
of the partition module).
