Added and applied the .gitignore file.
Created the calculator_button class for smaller buttons.

 On branch master
 Changes to be committed:
	new file:   .gitignore
	deleted:    build-calculator-Desktop-Debug/Makefile
	modified:   build-calculator-Desktop-Debug/calculator
	deleted:    build-calculator-Desktop-Debug/calculator.o
	deleted:    build-calculator-Desktop-Debug/main.o
	deleted:    build-calculator-Desktop-Debug/main_window.o
	deleted:    build-calculator-Desktop-Debug/qrc_qml.cpp
	deleted:    build-calculator-Desktop-Debug/qrc_qml.o
	deleted:    build-calculator-clang-Debug/Makefile
	deleted:    build-calculator-clang-Debug/main.o
	deleted:    build-calculator-clang-Debug/main_window.o
	deleted:    build-calculator-clang-Debug/qrc_qml.cpp
	deleted:    build-calculator-clang-Debug/qrc_qml.o
	modified:   calculator/calculator.pro
	deleted:    calculator/calculator.pro.user
	deleted:    calculator/calculator.pro.user.0051ea7
	deleted:    calculator/calculator.pro.user.73863d4
	new file:   calculator/calculator_button.hpp
	modified:   calculator/main_window.cpp
	modified:   calculator/main_window.hpp