The new class AppWell implements the application favorite well
in the Dash component. The previous AppDisplay remains for use
in the More... mode now.
Delete DEFAULT_APPLICATIONS; this is now in GConf.
Rename getMostUsedApps to getTopApps since we now have the
idea of explicit favorites.
Delete some GenericDisplay-related calls from overlay related
to the seletion - we'll reimplement keyboard nav in a more
coherent way later.