Collation support for fdb-record-layer using ICU.

fdb-record-layer-core includes a collate_jre key expression function that uses Java's built-in collation rules. Those are reasonably complete for normal use. But for the full Unicode Collation Algorithm, and a more complete choice of locales, ICU is needed. This artifact offers a collate_icu key expression function that uses it.

Packages 
Package Description
com.apple.foundationdb.record.icu
Use ICU4J instead of JRE Collator classes.