labs: add and use new cmd: queue

Add a new command, queue, to replace the old syntax in config/scripts.*.
Convert all config files to use the new syntax.

Previously, the scripts used hardcoded directory code words: scripts
for $SCRIPTS_DIR, osbash for $SCRIPTS_DIR/osbash.

With the new syntax, the argument is just a relative path inside
$SCRIPTS_DIR. This makes it easier to add (e.g. distribution-specific)
directories.

The new syntax makes also explicit that the command is used to queue
files for later execution.

Change-Id: I414b05785ad322e82f3bf3a38f3374d0e6c45c6c
Merge "labs: add and use new cmd: queue"