[manifest] Consider making display a space-separated list of tokens (#304)

http://w3c.github.io/manifest/#display-member

This is a bit speculatory, but on Android there are a lot of flags for different variants of fullscreen:
https://developer.android.com/reference/android/view/View.html#setSystemUiVisibility(int)

*If* there are aspects of display mode that are conceptually orthogonal *and* that can be controlled independently on Android and other platforms, it may make sense to separate these. If not, please ignore me :)

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/manifest/issues/304