Add custom support for A32NX

[sushiat]

• [ ] Check for useful custom simconnect variables/events
• [ ] Check if we can perform fuelling and loading automatically again
• [x] If not, provide guide/calculator on how to load the aircraft

[sushiat]

There are custom simvars for some missing aspects but they are all local and can't be accessed via external simconnect interface, added custom loading guide and pax/cargo calculator though