Keyboard improvements

Requesting feedback on this pull, which switches the browser app object to use the on-screen keyboard for entering URLs. This makes the interaction emulate the user more closely and avoids [bug 829514](https://bugzilla.mozilla.org/show_bug.cgi?id=829514) when certain characters are contained in an address.

I also added a 0.1 second delay when interacting with the keyboard so we have visual feedback for keys being tapped. Adding delays is not best practice, but I feel in this case the benefit could outweigh the cost.

Finally, I made the keyboard available to all apps by moving it from the base test to the base app. I feel this reflects the structure of Gaia much more closely, and should make it very easy to interact with the keyboard from within the app objects.

Looking forward to receiving feedback. I've tested all affected tests and they's passing on my inari with a recent (yesterday's) master build.