Add new koans about_control_statements

Add two new koans in about_control_statements

First koan is a loop if. We can compare if two numbers are equal or not. If is equal weĺl receive a message and if isn't equal weĺl receive a different message.

Second koan is a loop for. We have five numbers in the loop and we want to sum them all. Inside of loop for we have an expression with one condition that change this sum.