TMA- Add model class Track with volume property

Implemented a model class called Track to store a volume attribute
displayed by multiple UI elements. In the app delegate, declared a
property for a Track object. Accessor methods for the property are
automatically synthesized.

Add track class with property for volume control.
TMA- App core functionality

Implemented the methods of the app delegate that provide the app’s core
functionality—updating multiple views when the model data changes.
TMA- Add number formatter to text field

- Added a number formatter to the text field
- Fixed a problem when resizing the window by setting minimum size
constraint on window.
(note currently there are no constraints on ensuring the UI elements
stay centered)
BTD- TahDoodle Initial Commit

Simple to-do list app that stores its data as a property list.
Configured as a doc-based app so that users can have multiple windows
(each representing a different file) open at the same time.

Following Ch 32 - Your First Cocoa App from BNR Obj-C programming guide.
BTD- Add tableview and button to doc. Resizable.

- Setting up views (NSButton and NSTableView) with Interface builder.
- Adding auto layout constraints.
- Making connections to connect properties in our BTDDocument.h,
specifically to connect IBAction to ‘Add Task’ button, and have UI
tableView point to our IBOutlet.
- Implementing NSTableViewDataSource
BTD- Save and load data to file