Add a simulate only flag '--dry-run' to both CLI tx commands
and RESTful endpoints to trigger the simulation of unsigned
transactions.
* Turning --dry-run on causes the --gas flag to be ignored.
The simulation will return the estimate of the gas required
to actually run the transaction.
* Adjustment is no longer required. It now defaults to 1.0.
* In some test cases accounts retrieved from the state do not
come with a PubKey. In such cases, a fake secp256k1 key is
generated and gas consumption calculated accordingly.
Closes: #2110
Alessio Treglia
Joon
ValarDragon
Sunny Aggarwal
Alexander Bezobchuk