[TimePicker] display of 12 hour clock values is sub-optimal

[joewalker]

2 improvements:

• Don't have '0' padding for single digit hours. (i.e. 1:00 pm rather than 01:00 pm) For in-use examples, see the table at the top of https://en.wikipedia.org/wiki/12-hour_clock. As the 24h clock does do this '0' padding, this difference helps people recognise the time system in use
• Don't refer to 12:00 am or 12:00 pm; instead use 12 noon or 12 midnight. NIST: "12 a.m. and 12 p.m. are ambiguous and should not be used", or the Wikipedia article.

If this makes sense, I'm happy to make a pull request.