This solves several issues:
- use built-in default so that app monitoring is enabled when schemas are not installed
- don't start/stop timers without checking their previous state
- unreference the default GConfClient
- use #define for the GConf key path
ShellAppMonitor now depends on gmenu to load menus.
Use the menu data from ShellAppMonitor to show a menu list.
GenericDisplay implementations can now have a sidebar area. We
handle keystrokes such as left/right explicitly.
Some internal API changes to account for the fact that a display
can have another filter in addition to the search.
