Create settings model and cell model

Created a model for the Settings data stored in the plist. Also created an abstract class for the table view cells so cell subclasses can be exposed and manipulated through one class
Not true. If anything it's slower - it prevents against negative values. But we've had a bit of discussion on this in the dev team, and as of now,  CGRect accessor functions are *not* part of our official style guide. The conclusion being there are no significant advantages to readability or safety.