launcher: app-list-model
Extracted from !187 (closed) to get a more reasonable sized diff
What this does it quite simple really, it wraps G[Desktop]AppInfo/GAppInfoMonitor in an implementation of GListModel
The resulting list is updated for app installs/removals and only includes "should_show" apps ready to be fed into GtkFlowBox or other such widget to display apps
Intention is that a GtkSortListModel and GtkFilterListModel are used to sort the list and provide search