Update Part VI: Text fields.md
Merge pull request #31 from BillsJ/patch-1

Update Part VI: Text fields.md
Update Part VI: Text fields.md
Update Part VI: Text fields.md
Update Addendum I: History of Object-Oriented Programming.md
Update Part VII: Exercises.md
Update Part I: MyFirstWindow.md
Update Part I: MyFirstWindow.md
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