Add MediaRouter API to get presentation display.

This new API makes it possible for an application to ask on
which Display it should show a Presentation based on the currently
selected media route.

Also added a new API on DisplayManager to query displays that
support a certain category of uses.

Improved the documentation of the Presentation class to explain
how to choose an appropriate Display for presentation.

Bug: 7409073
Change-Id: Iab451215e570ae55f3718fc228303143c800fe51