Enhence error message "Not in Workspace"

The current message when one is not in the workspace on submitting solutions is not really helpfull.

Perhaps show the full absolute path of the first file that has the problem and also the configured workspace folder, eg:

```
Not in workspace.
File to submit: /Users/user/exercism/bash/hello-world/hello.sh
Workspace: /Users/user/Exercism
```

This way students could either carefully compare on their own, or they could copy paste the full error into chat/github/whatever.

This would reduce turnaround times, as the very common step of asking for the configured workspace would not be necessary anymore.