Message of the day was shown twice because the same bashrc.my file than
for containers was used. That file contained some code to show motd in
the container, where it is not shown by default. But in the VM, the motd
is shown by default, so it was shown twice.
Move the code to show motd to a file used only by nm-in-container and
not by nm-in-vm.
Also, modify the explanation about using prepare-for-system.sh because
it's only valid for Fedora but nm-in-vm can be used with other SOs too.
The script was generating the data-* files that later copies to the
container.
In order to the files being reusable for nm-in-vm, put them as separate
files inside the data directory.
However, some of the files need the full path to NetworkManager project,
which varies for each user. Instead, make a sed replacement on them and
generate the actual files that will be copied. Replacement:
{{BASEDIR_NM}} -> $BASEDIR_NM
Also, rename the files to more descriptive names, using some prefixes
that give a hint of where those files will be put, and the .in extension
to indicate that they will be processed.
