Improvement for IBC middleware pipelining as suggested by @damiannolan:

• Remove the ics4Wrapper field from 29-fee keeper and 27-controller keeper.
• Add extra next field of type porttypes.ICS4Wrapper to 29-fee IBCMiddleware and 27-controller IBCMiddleware, and a next argument to the corresponding NewIBCMiddleware constructor functions. We would have something like:

func NewIBCMiddleware(app porttypes.IBCModule, k keeper.Keeper, next porttypes.ICS4Wrapper) IBCMiddleware {
  return IBCMiddleware{
    app:    app,
    keeper: k,
    next:   next,
  }
}

• Replace in the implementation of the ICS4 wrapper interface in 29-fee and 27-controller the usage of keeper for next.