The RCC output files in version 2 contain a timestamp of the
source file, which changes per build. Drop down to version 1,
which just removes the timestamp.
See reproducible builds note 'timestamps in source generated by rcc'.
FIXES#917
Since we install the CMake files now, also put license headers in them.
These files are intended to help plugin and branding component authors
write them in a simple Calamares-idiomatic way.
