Allow Tint Color to be associated with a VectorDrawable

[benpious]

This is useful if a user is working with a predefined library of Drawables, such as our brand icons, and wishes to tint one in a different way before passing into a UI component that doesn't take a tint color with the Drawable. It doesn't make sense to add a new drawable only for the purposes of having a new color.

This also matches the API available in Android, though it's slightly complicated by the fact that in Android there's no such thing as a VectorDrawableView; The VectorDrawable is itself a View.

[CLAassistant]

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