functions --- main function library

functions-* --- function libraries for interface types,
protocols and features. These scripts usually understand
(or at least should understand) 'start' and 'stop' commands
and can perform both configuration and unconfiguration
respectively.

create-* --- plumb an interface
After one of those scripts finishes its work, there should be
a new interface available. It can have any name, we are going
to fix it later with iftab.

config-* --- protocol and feature configurators

setup-* --- post-config adjustments
These scripts perform some tasks, that need to be done in the
last turn. The interface is already properly named and has
undergone general configuration, when these scripts are run.

shutdown-* --- prepare for unconfiguration
These scripts are run before any other unconfiguration has place.

destroy-* --- unplumb interface
After these scripts finish their work, chances are high to not
see the interface in the interface table any more.
