ICU-21251 release icu4j.jar/utilities.jar to GH Maven
- on a release (created from Github), publish to
<https://github.com/unicode-org/icu/packages> as
1. icu4j-for-cldr
2. utilities-for-cldr
- also fix a doc bug in DecimalFormat
- this is intended for CLDR use.
- a tag such as 'cldr/2019-09-15' will turn into a
maven version '68.1-SNAPSHOT-cldr-2019-09-15'