[Usability]preference handling

[Stephan Bayer <s b gmx net>]

Often i read the need to give the user more settings. 

My idee,
we use a gconf key which stores normal user or advanced user (Default is
normal user).
Now we add a config Dialog to the control center where the user can set
this key. 

Every Application can read this setting and provide a Preference Dialog
fitted for the user skills. 
If there is no need to do this (cause only 2 settings or no time, ...)
the application should provide a dialog for normal users.