FluxTraining.resolveconflict

			resolveconflict(cb1, cb2)

Define a conflict resolution strategy for resolving a write/write conflict
between two callbacks.

The default is [ NotDefined() ], which will result in an error and a message
to implement this method.

To implement, dispatch on the callback types that you which to resolve (in any
order) and return one of the following:

• Unresolvable () if the callbacks must not be used together

• RunFirst (cb) if one of the callbacks needs to run first; or

• NoConflict () if the callbacks may run together in any order