Only do updates to the history list once every 10 seconds.  Also only show notifications once every 45 seconds at the most often.  Otherwise the UI will lock up when large wallets are updated/synchronised.  Fix #817
Only do updates to the history list once every 10 seconds.  Also only show notifications once every 45 seconds at the most often.  Otherwise the UI will lock up when large wallets are updated/synchronised.  Fix #817

fyookball/electrum,fyookball/electrum,fyookball/electrum