Location services and safari capabilities

Lots of stuff here:

- allow toggling location services system wide with `locationServicesEnabled` cap
- allow toggling location services for AUT with `locationServicesEnabled` cap
- various Safari-specific capabilities:
  - `safariAllowPopups`: true/false
  - `safariIgnoreFraudWarning`: true/false
  - `safariOpenLinksInBackground`: true/false

These all involve plist hacking which assumes the simulator dirs and in some cases the app specific dirs are present. So if they're not, we briefly launch instruments and then kill it to create the dirs. Unknown whether this is enough for the app-specific dirs at this point.

I've added tests for these, but please pull and test before we merge!