Implementations of chrome.system.cpu|display for ios

- Add auto tests for chrome.system.cpu plugin
- Initial stub implementation of chrome.system.cpu.getInfo for ios
- Add auto tests for chrome.system.display plugin
- Implementation of chrome.system.display.getInfo for ios
(Minor style preference)
I'd probably put this inside of the `describe('getInfo')` block below, with a spec description of just "should exist". "should have getInfo exist" sounds odd to me :)