The btcscript API for GetSigOpCount and GetPreciseSigOpCount
recently changed to no longer return an error. This change was necessary
to mirror the behavior of bitcoind signature operations counting. This
commit modifies the code accordingly to use the new API.
This commit modifies the double spend detection to handle double spends
within the same block as well as side chains when doing the checks before
reorganizing the chain.
This commit modifies the code to use params based on the active network
which paves the way for supporting the special rules and different genesis
blocks used by the test networks.
