make useradd -m create ~/.bashrc as file, not as symlink pointing to the store

For /etc/skel/* files put file contents into user directories rather than
"symlinks". This way users can edit their .bashrc files.

This small patch works fine with the multi-shell-support topic branch found on
my github page which rewrites .bashrc and similar files to source /etc/ files.
Thus users can opt-out or set options - still following system updates.

Signed-off-by: Marc Weber <marco-oweber@gmx.de>