Capitalize and punctuation in the settings dialog options

• Only first letter is capitalized in the options - logical but: except for the button, title items
• Forget the two colons character in the options (text fields, dropdown boxes, etc.)

See a38047c8 as example.

I always use the Catalan language version, and I see what happens in other dialogues.

Reference: https://develop.kde.org/hig/style/writing/capitalization/