Runtime module override

[magyarosibotond]

I'm trying to cover a use case when the root module needs to be rebuilt due to an API environment change. Once the network client changes, the affected modules should be redefined.

In Koin there's a loadKoinModules that lets the developer replace affected modules after startKoin is called (reset cached data when the user logs out).

Let me know if you had something similar in mind and I'm happy to contribute.

This would also fix #42