[v6r11] Splitting os compatibility

The /Resources/Computing/OSCompatibility section of CS has been split in 2 parts (maintaining backward compatibility using the Resource Helper): 
- Platform -> OS relation in /Resources/Computing/PlatformsToDistribution
- Platform -> SystemConfig relation in /Resources/Computing/PlatformsToConfigs

The helper used everywhere needed. An explanation within the wiki "what's new? how to update?" will follow.