Hello,
this PR closes #39.

There was a request to add a new word casing option that would convert a ONE word to upper case.
I believe this is a reasonable addition, especially to satisfy the "at least one upper case letter" requirement.

The new option in word casings:

Example generated passwords:

(~ is a separator)

mixes~mowed~tempt~fats~ANNE
ocr~PAGAN~obit~plank~berra
BLEAT~bog~dressy~ma~among

Notes:

• The new option is implemented on lines 213-216 in Diceware.cs.
• I reorganized the ApplyWordCasing function to make it a bit simpler (at least for me). Where the ApplyWordCasing function handles one off changes, and a second function ApplyWordCasingAcrossMultipleWords (that is called from the main ApplyWordCasing) handles changes where we need to iterate over every word.