Move Configuration creation from Window Manager to Activity Manager.

Currently the construction of configuration is split between thease
two entities. This poses two problems: it's harder to follow the
construction logic and more importantly we can't determine if
configuration changes significantly before delegating work to the
Window Manager. This CL moves the configuration override logic to
the Activity Manager, since it both detects configuration changes and
informs clients about them. Window Manager becomes purely a recipient
of the information.

Change-Id: I075570ee055cce9c5665772fa8d4fe8ccb5c6313