Configuration UI Improvements

Here we collect UI improvements for the configuration screens:

• the cancel and save & close buttons should be next to each other
• the save button doesn't really need the "& close" part as the save action already closes
• hitting return within an edit field creates a new line, without resizing the field, thus making it appear blank
• pressing tab in an edit field should move to the next field, not insert a tab at the cursor position
• Add CMD-Enter to save & close the dialog
• Validate and pretty print the default JSON value (it's taken as-is from the default string at the moment)
• Use a monospaced font in the JSON textbox
• Move the description field above the input field (at least for the json field?)
• Add "info" type object (would be used to display static text, whatever is in the description property. My desires are to display some information for a given section.