Cleanup of platform handling

- Used centralized handling of platform type, avoiding duplications of "The Android Project" magic String

- Removed PlatformStrategyFactory, as it anyway was not used
consistently, and as the strategy depends on the input types.


Remark: Even if we'd like to keep PlatformStrategyFactory, it would make sense on the one hand to use a centralized place to determine the platform (such as PlatformStrategy.platformType()), and on the other hand to make the strategy dependent on the input types.