Allow use of display names over logical names for steps

## Is your feature request related to a problem? Please describe
Using display names makes tests more readable, an example where this would be useful is in the below steps:
```
When I enter 'test' into the 'new_textfield1' text field on the form
Then I can see a value of 'test' in the 'new_textfield1' text field
```

## Describe the solution you'd like
It would be useful to query the logical name of a field from the user provided display name, rather than forcing them to find out and use the logical name in tests:

```
When I enter 'test' into the 'Description' text field on the form
Then I can see a value of 'test' in the 'Description' text field
```