Watched spending: don't import to watching wallet

[Kexkey]

We don't need to import an address from the spending wallet to the watching wallet to be able to watch it; every address of the node's wallets will trigger a walletnotify action.

Currently we systematically import a watched address to the watching wallet even if it's a spending address, so we have a lot of addresses in both wallets for no gains.

[phillamy]

Added optional callback urls to getnewaddress so CN can add a watch in a single call. The clients won't have to call getnewaddress followed by a watch request of this newaddress anymore

[Kexkey]

Did you also remove the importaddress to the watching wallet when trying to watch a spending wallet address?

[phillamy]

Can't find those changes locally. Maybe changed my mind also : let the caller do the 2 calls and wrap those 2 calls into something called watchNewBitcoinAddress