* Fix exit codes:
- `--help`, `--version` etc should exit with `0` i.e. no error ("not enough args" case should still trigger an error)
- error reading config file should exit with error
- slightly refactor AppInitRPC/AppInitRawTx to return standard exit codes (EXIT_FAILURE/EXIT_SUCCESS) or CONTINUE_EXECUTION (-1)
- every main()/exit() should return/use one of EXIT_ codes instead of magic numbers
