<i18n dev> Additional Date-Time Formats

[Naoto Sato]

Hello,

I am proposing a couple of new factory methods in 
java.time.format.DateTimeFormatter that produce flexible localized 
date/time formats, other than the existing pre-defined 
(FULL/LONG/MEDIUM/SHORT) styles. For example, if the user wants a year 
and month only string, such as the title for the calendar, currently 
they would have to use DateTimeFormatter.ofPattern() with explicit 
pattern argument, such as "MMM y". This is problematic because it is 
correct in locales such as US, but not correct in other locales.

So, I propose methods that are parallel to ofPattern(), which take 
pattern template. This is based on the CLDR's skeleton: 
https://www.unicode.org/reports/tr35/tr35-dates.html#availableFormats_appendItems

Detailed design can be found in the draft CSR: 
https://bugs.openjdk.java.net/browse/JDK-8243445

Comments are welcome.

Naoto