Combine multiple arguments into a JSON array

In an attempt to remove JSON from the standard CLI interface, the user needs to construct arrays of strings. This commit allows users to use e.g. `--tag tag1 --tag tag2` to construct the JSON array `{"tag1", "tag2"}` when passed to the server.
Allow JSON object syntax `name=val`

In order to remove JSON from the `create-broker` command's `--configuration` parameter, there needs to be an alternative way to construct the JSON object that's passed to the server. The user can now provide any argument as `--argument name=value` and the client will construct the JSON object passed to the server.

Fixes https://tickets.puppetlabs.com/browse/RAZOR-198