Improve error messages for web actions

I'm recording this "feature request" since it came up a couple of times on the open Slack.

My example relates to an action for which I forgot to use the `--web true` flag. When I tried accessing the action from the browser, the error reported was that this resource doesn't exist. This error message was puzzling because I was sure I had created the action. It took me a while to figure out that I forgot to enable it as a web action.

A different user reported a slightly different problem. He tried submitting to an action a parameter that had a default value (i.e., it was declared part of the action creation). Excerpt from Slack conversation:

```I added a default param to a web action. Now when I try to pass that parameter through the URL I get `{
“error”: “Request defines parameters that are not allowed (e.g., reserved properties).“,
“code”: 179565
}```

It turns out this is a feature not a bug. I guess we could improve the error messages (or the tooling around it? or both?).