Create pbj-while-loop-goal1

# Goal #1: Write a new version of the PB&J program that uses a while loop.  Print "Making sandwich #" and the number of the sandwich until you are out of bread, peanut butter, or jelly.

# Example:
# bread = 4
# peanut_butter = 3
# jelly = 10

# Output:
# Making sandwich #1
# Making sandwich #2
# All done; only had enough bread for 2 sandwiches.