Fix Region Dependant Parsing on UMAProperties

[ccouprie]

I realized some users of my game had their character being invisible, I identified that it was because they had their computer region settings in German Switzerland (float format being 1'000'000,00) and other countries had similar issues. So I checked and in the UMAMaterialPropertyBlock the parsing of the color properties depends on the region settings of the player when the writing of the color properties is done accordingly to the dev's region settings.

So I added CultureInfo.InvariantCulture to the parsing and the writing to make it region independant

[Jaimi]

Manually merged against incoming changes, will appear in next update.