Use annotated command syntax for most shared commands

The patch updates most admin shell commands shared by most services
to the annotated command syntax. This provides nicer help output and
avoid that services like pin manager and space manager show a mixture
of old and new help styles.

The command scanner had to be extended to supported inherited commands.

The help command has been turned into a real command, which means
it will appear in the help output and has a help page too. To avoid
that it gets included multiple times due to being inherited multiple
times, I made the help command optional in the CommandInterpreter.
CellAdapter and UserAmdinShell enable it.

The save and reload commands are now only loaded in services that
actually support these commands.

Target: trunk
Require-notes: yes
Require-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/6531/