Support Blueprint Nativize

[brwarner]

Previously, the plugin generated non-compilable C++ code when using Blueprint Nativize. There were two culprits.

1. A method on IArticyReflectable which shared its name GetClass with a method on UObject, creating an ambiguous call.
2. A number of BlueprintCallable methods which were protected, not public, creating compile errors (it seems protected variables are fine though, as nativize builds a workaround).

There may be more issues, but I haven't identified any more in testing.