display time taken for mining, processing blocks

updated to log the timestamp when block is found and time it takes for processing it.
The block (hash, height, number of transactions) and the total number of available utxos which all actors from the simulation can spend are two different things.  I'd recommend separating the logging like this:

"Block 123TheHash (height 123) attached with 234 transactions"

"345 transaction outputs ready to spend"

That last line could use some love still I think, but imo the block logging is much better.