Let feature + metadata textures make copies

[j9liu]

This change looks a lot more intense than I intended to be, but here's a summary:

• Created TextureView base class that FeatureIdTextureView and PropertyTexturePropertyView now inherit from. This is copy pasting the common code from both implementations.
• Added TextureViewOptions, which includes the applyKhrTextureTransform flag from a previous PR. But now it includes makeImageCopy, which makes a CPU copy of the input image if true.
• Added options parameter to various PropertyTextureView functions so that property views could be constructed with the desired options.
• Added unit tests for the new options.

[kring]

Looks good! A few suggested tweaks below. Actually, it's mostly just the one suggestion repeatedly.

[j9liu]

Thanks @kring ! Merging with your approval.