launcher: Clip list view

Avoid dragging icons outside the element.
libhawaiishell: Don't populate the applications model on creation

This saves some time when the model is created.
appchooser: Ask the applications model to populate when ready

Populate the applications model when the component is completed.
server: Expose panel's view

Expose the weston_view that corresponde to the panel so that elsewhere
we can check whether a view is a panel or not.
client: Set panel config view position according to available geometry

Consider the available geometry even if at the moment qtwayland doesn't
support it.
client: Move config view when panel size changes

Follow panel even when its position is changed.