yFiles 3.X

[EJ-K]

These changes aim address breakages resulting from the upgrade from yFiles 2.X to 3.X. The majority of these changes are deletions of fixes/"hacks" to types/methods that no longer exist. Changes were also needed to address the removal of yFiles' custom type system (e.g. YObject, YClass, $class). Additionally, these changes update the format of the resulting Kotlin code to bring it more in line with the Kotlin style guide.

Additional context:

• No real effort has been made to update yfiles-kotlin examples/documentation.
• These changes don't offer any dedicated support for new yFiles features, they primarily just fix breakages in the generator.
• Testing of these changes is limited to our (somewhat limited) uses of the library.