Refactor|LabelWidget: Rules for expansion

Internally, the width and height rules may be either the grow
animation rules or the constant rules describing the true size of
the content.
Refactor|libappfw: Use pimpl-friendly audiences for libappfw classes

All use of libappfw classes updated accordingly.
UI|Client: Handling a failed direct query for servers
Fixed|libgui: Unsigned math issue in window centering

Trying to center a window larger than the desktop would produce
invalid coordinates.
SDK|Unix: Deploy SDK libs to built app using symlinks

Todo: This should be an optional feature, though.
Refactor|ClientApp: Moved font related script bindings to BaseGuiApp