Enhanced OSVersionInfo with a SimpleOSLevel.

- Goal is to ease version detection.
- Removed useless stuff (duplicates of OSVersion properties).
- Removed useless "Edition" support (after having updated Product enum).
Enhanced OSVersionInfo with a SimpleOSLevel.

- Goal is to ease version detection.
- Removed useless stuff (duplicates of OSVersion properties).
- Removed useless "Edition" support (after having updated Product enum).
Added comments & test success of PInvoker emitted type.