This commit changes the code generator to generate a `UnmarshalJSON` for each
struct, so that if unmarshalled it properly handles UniFis varying integer values
via the `emptyStringInt` type.
Structs not including a field of `int` type will still have the function generated,
but it will effectively do nothing.
Fixes#18
* Allows for specifying more customizations per field in each type.
Previously, the switch clause didn't allow sub-types to be modified, but
that became a problem with some of the more complex types.
* Fixed several problematic fields in the Device resource
* Removed the underscore separator from generated type names
This allows callers to create complex payloads; for example, to create a
Device type for a Unifi Switch with PortOverrides, the caller needs to
create these sub-types, which is not possible when it's purely embedded.
