Update translatable source strings to use consistent quotation marks:

• Review strings containing quotation marks on  whether those are necessary
• Consistently use one style (double or single quotes) as primary. As Picard's UI is (or is supposed to be) American English the double style is probably what should be preferred (see https://en.wikipedia.org/wiki/Quotation_marks_in_English)
• Use typographic “ ” quotes instead of ASCII. As this is about written text it fits better. Many translations already use typographical correct quotes, e.g. French uses « » and German „“. Also it avoids escaping inside of strings.