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 generating top-level types for any embedded struct so
that sub-types can be properly instantiated from calling code
* Specifying `-no-embedded-types` will generate top-level types
rather than embedding the struct
* Refactored "Device" API
* All fields set to `omitempty` because it describes all possible
device types, so effectively any field could be omitted any time
* Fixed `get` call for "Device" API; replacing `rest` with `stat`
* Generated `get` and `update` calls for `Setting*` APIs
* Added `5.14.23` JSON files
