The CAmount name is not helpful as its just an int64_t and not a
class, like the name implies. There were a handful of places where
it was passed in as const-ref, as a good example of this actually
creating sub-par code.
This removes the attempt at magic (predicting future) component
called the fee-estimator.
The direct effect is that all transactions have as a mempool acceptance
the same minimum fee. Regardless of how full the mempool or blocks were.
This mempool-acceptance minimum fee is 0 sat/byte. (aka free)
Notice the node-wide free-tx accept-limiter is going to avoid us getting
overloaded.
The "UAHF" one used to be "more equal", mostly just because it happened
to be the first.
This makes them all equally equal.
Specifically this removes the special casing and the enum for the 201708
HF (aka BCH fork-point).
We select the right branch now purely based on the historical check-
points.
tomFlowee
TomZ