In this commit, we add the current chain parameters to the
BitcoindNotifier. This will be used in a future commit in order to
convert outputs scripts into addresses. This is needed since the
bitcoind backend uses these addresses to detect whether the script
encoded within it was spent by a transaction in the chain.
In this commit, we introduce a nice optimization with regards to lnd's
interaction with a bitcoind backend. Within lnd, we currently have three
different subsystems responsible for watching the chain: chainntnfs,
lnwallet, and routing/chainview. Each of these subsystems has an active
RPC and ZMQ connection to the underlying bitcoind node. This would incur
a toll on the underlying bitcoind node and would cause us to miss ZMQ
events, which are crucial to lnd. We remedy this issue by sharing the
same connection to a bitcoind node between the different clients within
lnd.
