* eth, miner: fix enforcing the minimum miner tip
* ethclient/simulated: fix failing test due the min tip change
* accounts/abi/bind: fix simulater gas tip issue
* accounts, ethclient: minor tweaks on the new simulated backend
* ethclient/simulated: add an initial batch of gas options
* accounts, ethclient: remove mandatory gasLimit constructor param
* accounts, ethclient: minor option naming tweaks