multi: add rpcpolling config options

sample-lnd.conf

@@ -606,6 +606,14 @@ bitcoin.node=btcd
 ; bitcoind.zmqpubrawtx=tcp://127.0.0.1:28333
 ; bitcoind.zmqreaddeadline=10s
 
+; Use bitcoind's rpc interface to get block and transaction notifications
+; instead of using the zmq interface. Only the rpcpolling option needs to
+; be set in order to enable this, the rest of the options can be used to
+; change the default values used for this configuration.
+; bitcoind.rpcpolling
+; bitcoind.blockpollinginterval=1m
+; bitcoind.txpollinginterval=30s
+
 ; Fee estimate mode for bitcoind. It must be either "ECONOMICAL" or "CONSERVATIVE".
 ; If unset, the default value is "CONSERVATIVE".
 ; bitcoind.estimatemode=CONSERVATIVE
@@ -814,6 +822,14 @@ litecoin.node=ltcd
 ; litecoind.zmqpubrawtx=tcp://127.0.0.1:28333
 ; litecoind.zmqreaddeadline=10s
 
+; Use litecoind's rpc interface to get block and transaction notifications
+; instead of using the zmq interface. Only the rpcpolling option needs to
+; be set in order to enable this, the rest of the options can be used to
+; change the default values used for this configuration.
+; litecoind.rpcpolling
+; litecoind.blockpollinginterval=1m
+; litecoind.txpollinginterval=30s
+
 ; Fee estimate mode for litecoind. It must be either "ECONOMICAL" or "CONSERVATIVE".
 ; If unset, the default value is "CONSERVATIVE".
 ; litecoind.estimatemode=CONSERVATIVE