added python file

Python file for comparing two Excel file, all sheets with the same name,
all cells in the same absolute position in both files, comparing
formulas instead of values. The program reports in plain ASCII on each
sheet with differences and a report on all differences can be saved as
text file. It also has a currently disabled option to show the changes
in the first Excel file by highlighting cells with differences and
adding a comment that compares the formulas of the two Excel files.