[icu-design] Convenience methods on DateFormat

[Mark D. ☕ <ma...@ma...>]

I would like to propose the following API for: *ICU 49*
Please provide feedback by: *Tuesday, 2011-12-20*
Designated API reviewer: *Yoshito*
Ticket: http://bugs.icu-project.org/trac/ticket/8960

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Many people don't realize that ICU offers very flexible date and time
formats. And the code can be cumbersome, using a DateTimePatternGenerator.

I suggest adding the following convenience methods:

static DateFormat	getInstanceForSkeleton(String skeleton)
static DateFormat	getInstanceForSkeleton(String skeleton, Calendar cal)
static DateFormat	getInstanceForSkeleton(String skeleton, Calendar
cal, Locale locale)
static DateFormat	getInstanceForSkeleton(String skeleton, Calendar
cal, ULocale locale)

Internally, these would create a DateTimePatternGenerator, and call
getBestPattern(String skeleton), then create a SimpleDateFormat with that
pattern.