Issue 66 - Added option to disable preferred location

Added isPreferredLocationEnabled option as per #66.

Tried to add a jasmine test for the change from "Other locations" to "Recent locations", first by checking the html for the string and then by spying on translations, it worked in browser but not through the command line.  I gave up and deleted the test.

Storing the "isPreferredLocationEnabled" in the userLocations object only (not duplicating in controller).  This means that the cold start check in the controller looks into userLocations, not sure if this is desirable?

Need to update the pull request for the welsh translation when I get it but thought I would create this now to give it more time to be reviewed.
I think you are looking for ``!!``

Undefined:
```
> var options = {};
> !!options.isPreferredLocationEnabled
false
```

True:
```
> var options = { isPreferredLocationEnabled: true };
> !!options.isPreferredLocationEnabled
true
```

False:
```
> var options = { isPreferredLocationEnabled: false };
> !!options.isPreferredLocationEnabled
false
```