Support for embedded Object declarations

[jakobmygind]

Not the prettiest string manipulation, but it seems to work with struct and final class

[dominik-hadl]

Thanks for the changes, this will be a great addition!
There's just a few things that need to be fixed before we can merge this :)

1. Remove @objc from declarations unless absolutely necessary (ie. for performSelector or timers..)
2. Remove or fix commented out code. There's also no fixmes/todos so it will just get forgotten in the future and it looks bad in the code.
3. Update travis to compile properly for Swift 4
4. Can you please write a summary of what exactly has been changed and how? The current description and code changes are impossible to understand for anyone who doesn't know the codebase already.

Otherwise can't wait and will merge asap! 🎉

[jakobmygind]

Changes: Instead of throwing an error when locating several declarations within one model, we now first extract the embedded model then recursively extract the remaining occurrences
and prefix the model name with the parent's name plus ".". The model strings are then passed to the model generator one by one, and the results are concatenated.