Implementations of chrome.system.* for ios (cpu, display, memory, network)

- 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
For this and the others - Don't bother with a .h file since there are no useful symbols being exported. Just cut & paste the `@interface` into the .m file.