Our node didn't respect the MaxPeers setting, fix it with a drop of random
connection when this limit is reached (to give a chance for newcomers to
communicate), but also introduce AttemptConnPeers setting to tune the number
of attempted connections.
This also raises the default MaxPeers for testnet/mainnet to 100, because
neo-go nodes love making friends.
This one enables our RPC to be called from the browser if there is a
need. It's insecure and not standards-compliant, thus this behaviour is
configurable is not enabled by default. It makes our node with this workaround
enabled compatible with neo-mon monitoring.
Originally debugged by @anatoly-bogatyrev in #464.
Enable transaction verification for privnets and tests, testnet can't
successfuly verify block number 316711 with it enabled and mainnet stops at
105829.
