Update liquidity script for new command formats

[peterbarrow]

The old liquidity command was used for creating, amending and cancelling a liquidity provision. That has changed now as we have a separate command for each action. This ticket is to update the existing scripts to only create a new LP and to add 2 more sets of scripts for performing amending and cancelling.

[candida-d]

Since pegged orders are undergoing similar changes, this would be a good issue/PR to also incorporate those changes (as discussed with @peterbarrow)