Refactor ctclient command-line tool

- [x] #901
- [ ] Clean up the code of each subcommand
- [ ] Support intuitive positional parameters, e.g. `get-consistency-proof 100 200` instead of `get-consistency-proof --flag_for_first_size=100 --flag_for_second_size=200`.

Start with the ctclient command-line tool and review the implementations of each subcommand, especially get-consistency-proof and its current parameters. Done means the subcommands are cleaned up and get-consistency-proof accepts intuitive positional values such as 100 and 200 instead of the two flags.

Written by the indexing model from the issue text.