Implementation of composition structural design pattern

[shaynmorgan]

Major Changes

• Redesigned the Coordinate class to implement the composition design pattern, by creating a Longitude and Latitude class.
• The Longitude and Latitude classes are symmetrical and serve a very similar purpose on the client-side. Therefore, using the composition design pattern is justified.
• Longitude objects can be added to other Longitude objects via the sum() function and the same is true for Latitude objects.
• Longitude objects can be added to other Latitude objects via the merge() function and results in a 'Coordinates' object.

Minor Changes

• Updated constructor of Coordinate class to use Longitude and Latitude objects
• Also updated all calls of the constructor in other classes to reflect new changes
• Updated the implementation of str() in the Coordinates class to reflect new changes