Added license.txt

Text file with the project's license conditions.
Added Py_Calculate readme.md

Readme file includes all the necessary information about the project.
Added Python Excercises.txt to root

List of all upcoming projects to complete!
Added Py_Calculate.py file to project

Source file
Added main Py_Calculate.main.py to project

The main source code for Py Calculate. The current source is in its
finished state and will no longer be worked on in the future.