Update frame selection with respect to spectator view ping time. (mic…

…rosoft#159)

Merge pull request microsoft#144 from fieldsJacksonG/master

Update spectator view to the latest HoloToolkit (1.5.7)

Spectator view bug fix - preview window DPI awareness.

microsoft#91
Change preview window to a dropdown instead of a popup for better DPI awareness.
For best results, the windows taskbar will have to be hidden.