Fix incorrect metadata property values being sent to material

[j9liu]

In our metadata handling code, I found some unfortunate typos that happened as a result of overzealous copy-pasting. For some reason the encodedProperty.offset value was being passed for the scale, noData, and default value properties, which is obviously wrong. 🙃 Plus, I had typoed a + sign as an = sign, so one parameter was never being set.

This PR does two things:

1. Fixes the aforementioned bugs
2. Moves the Set____ParameterValues functions from CesiumGltfComponent.cpp to CesiumEncodedFeaturesMetadata.h. This was not strictly necessary, but I think this organization is helpful for decreasing the complexity of CesiumGltfComponent, and for putting the code closer to the rest of the CesiumEncodedFeaturesMetadata functionality.

If you'd like, you can verify that these values are passed correctly using the CesiumJS sample dataset in Specs\Data\Cesium3DTiles\Metadata\StructuralMetadata. Notably the employeeCount, year, and temperatureCelsius properties will be affected.

For temperatureCelsius you can reproduce this result with these material nodes:

Result	Nodes

You can also get the same result by dividing the Raw Value by 255, and lerp-ing that.

For year you can reproduce this result with these nodes, though it simply tests that the default value is passed in.

Result	Nodes

For employeeCount you can reproduce this result with these nodes:

Result	Nodes

[kring]

Looks good, thanks @j9liu!