Important modification to enable extending each lines in csv data:
Add copyright claim and simple description of this program.
Modify file_save() to show message correctly.
Remove useless comma at the end of each line: (Very good changes)
Add focus_set() to easily edit the text: entryedit.focus_set()
Enable bind for Ctrl+A and Ctrl+D to quickly add row and delete row.
Add undo=True in Text() of ui.py
Initial commit