Added 02 Loops functions

Part of Fullstack prework week 2 assignment.
Added 03 Calculator functions

Part of Fullstack week 2 prework.
Moved 03 Calculator functions to constructor

Functions and initial 0 value were being declared for the prototype; moved them into to the constructor for Calculator.
Refactored 02 Calculator

Moved functions to prototype and value initialization to constructor.
Refactored 02 Loops

Cleaned up code, used join function where allowed.