Allow to send a directCommand to the Ocean Node, for testing purposes

[paulo-ocean]

We still don't have any support for sending a directCommand to the node. This could be very useful for testing many features.
The idea is to have a new command on the CLI (the directCommand), where we just specify the input from a JSON file
Some commands might require additional work, like for instance the ones needing a signature.. or the ones requiring a nonce (we need to get the correct one first)