Clearer Tracing

Trace logging similar to the following;

```
Error
    at isProtectedPage (chrome-extension://dcjnfaoifoefmnbhhlbppaebgnccfddf/lib/background.js:460:9)
    at Object.callback (chrome-extension://dcjnfaoifoefmnbhhlbppaebgnccfddf/lib/background.js:346:20)
    at Object.chromeHidden.handleResponse (sendRequest:49:24)
```

Can be confusing because of the "Error" heading. This PR replaces this heading with "Trace". For example;

```
Trace
    at isProtectedPage (chrome-extension://dcjnfaoifoefmnbhhlbppaebgnccfddf/lib/background.js:460:9)
    at Object.callback (chrome-extension://dcjnfaoifoefmnbhhlbppaebgnccfddf/lib/background.js:346:20)
    at Object.chromeHidden.handleResponse (sendRequest:49:24)
```

Simple change but effective.