Add color mode to activity/window

The color mode lets an application request a wide color gamut for
a specific window. This will also be used in the future to request
HDR. The color mode is currently either default (sRGB) or an undefined
wide gamut color space chosen by the platform. These attributes could
later be used to choose a specific color space if we deem this important
or useful.

This change also renames the various "colorimetry" attributes and
constants to "color mode" for consistency. These symbols were
added in O and can be safely renamed.

Test: CtsColorModeTestCases
Bug: 32984164
Change-Id: I4d4691dd12dbe3f3aa6a5cf893cff39aa16c739e