Mac OS X: Move settings to preferences

[joshgerdes]

Move settings from Edit menu to main app menu and rename to preferences to conform to Apple's Human Interface Guidelines. Added associated keyboard shortcut.

https://developer.apple.com/library/mac/documentation/UserExperience/Conceptual/OSXHIGuidelines/MenuBarMenus.html#//apple_ref/doc/uid/20000957-CH29-SW3