Add RNtuple support to the QwCorrelator class.

[paulmking]

The QwCorrelator class does not support creating an RNtuple, it just has support for creating a TTree.

[wdconinc]

@dimensional-difficulties Can you look into this? These correlations are one of the things we want to be able to validate against the mock data input.

@paulmking Do we want QwCorrelator to use QwRootFile etc instead of using its own stuff?

[dimensional-difficulties]

Pending

[wdconinc]

#191