Properly apply dependency injection / inversify

We have a rather massive constructor for the main engine (KiiGame) class.

Our inversify config covers two classes at the moment as a POC.

We should configure the dependencies with inversify.

Scope:
* configure all default dependencies with inversify
* do the Lätkäzombit-specific configurations/overrides with inversify
* (maybe in scope): implement building Lätkäzombit assets & extra features with inversify instead of accessing KiiGame class instance properties

Start by inspecting the KiiGame constructor and the existing inversify configuration for its two proof-of-concept classes. Map the default dependencies and Lätkäzombit-specific overrides before deciding how assets and extra features fit. Done means all default dependencies and game-specific configurations use inversify; asset construction is included only if its scope is confirmed.

Written by the indexing model from the issue text.