Support for --format argument on search command

[davideavanzi]

Currently, the keeper search command does not support different output formats other than tabular data.

As an example, it is possible to run the keeper list --format=json command to obtain the whole vault in a JSON format, but it's not possible to have the same output for the keeper search one.

In fact, running keeper search --format=json search_term returns the following error:
unrecognized arguments: --format search_term

[sk-keeper]

Commander supports --format argument for commands with table-like output.
search command output is not a table though it can be redirected to json format.
There are list, list-sf, and list-team commands that support --format argument.

[davideavanzi]

I understand, I was supposing that the search output was mostly the same as the one of the list command, so I thought that a JSON-formatted output might be useful.