some minor tweaks to cleos output & read only actions

[spoonincode]

For ROtrx I suggest we remove the

warning: transaction executed locally, but may not be confirmed by the network yet

output at the end of cleos. The text is clearly not right for a ROtrx.

I also think we should do something with the 0 us that is always printed, either

• don't print resource utilization at all (including NET), since it doesn't really matter for ROtrx
• use populated elapsed for displaying the output here
• fix nodeos to populate cpu_usage_us for ROtrx? Not sure what to think about that

[heifner]

• cpu_usage_us is short for billed_cpu_usage_microseconds, nothing billed here, so probably better to leave that at 0.
• I like the idea of cleos printing elapsed and not net, since net also implies billed amount.
• I think we want the JSON output to show no net or cpu_usage_us.