Make all C# flavors support x-zero-based-enum and add tables to documentation

[EraYaN]

This makes all other C# flavors also support the x-zero-based-enum vendor extension and it documents it.
Arguably the enums should be some tuple with an actual value field so the Java code can have full control, but this will work for now.

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EDIT: The build works now and everything has been committed.

[wing328]

EDIT: Alright GlobalSettingsTest fails because item 345 does not equal test2 but null, but in the dump you get it does appear. Not sure how my changes can break this.

i think that's fixed on the latest master

can you please pull the latest changes in the official master into your branch?

[EraYaN]

Alright so the build works now, that also made me realize where to add the vendor extensions so the docs update correctly.

[wing328]

cc @devhl-labs as well who maintains the C# generichost (default) client generator