Add RasterBand's colour interpretation

[shuternay]

• I agree to follow the project's code of conduct.
• I added an entry to CHANGES.md if knowledge of this change could be valuable to users.

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This PR adds methods for reading and setting RasterBand's colour interpretation. It also adds methods for getting interpretation value name and getting interpretation value by name.

P.S. I'm not sure how to achieve this, but shouldn't mutable borrow of RasterBand require mutable borrow of it's Dataset?

[jdroenner]

please look at the exports / imports and remove the "get_" prefix. Also please resolve the merge conflicts.

[shuternay]

I've added an enum for color interpretations (should resolve problems with free methods and imports) and resolved merge conflicts