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
This is short for [NSString stringWithUTF8String:value]. Aka, a memory leak.

You could use [[NSString alloc] initWithBytesNoCopy:length:encoding:freeWhenDone:] instead, or free() the memory yourself.