make_module: do not exclude big directories

make_module would exclude any directory which was included
in previous module and has subdirectories
Load all the modules from grub.cfg
Run post-install.sh before building lists

package and file lists should include changes made by the
post-install.sh script.
initramfs improvements

- separate some code to functions.sh
- use templates (*.pldnrt) in the initramfs 'skel'
- load all the modules, not just 'base'