Add c# style async/await functionality

[jmaine]

It would be nice for lombok-pg to add c# like async/await functionality:
https://msdn.microsoft.com/en-us/library/hh191443.aspx

It would require to turn the method into a state machine like a generator.
https://github.com/peichhorn/lombok-pg/wiki/Yield

[lbrasseur]

This would be great. There is one implementation from EA:

https://github.com/electronicarts/ea-async

And other one:

https://github.com/vsilaev/tascalate-async-await

(BTW, I tried to run EA implementation in Android and I couldn't make it work, maybe an annotation processor based implementation would make this easier)