Updated ADBA (Async DataBase Access) source

[Douglas Surber]

Lance uploaded the latest update of ADBA to the JDK sandbox.

  http://hg.openjdk.java.net/jdk/sandbox/file/b49fd5dbaab6/src/java.sql/share/classes/java/sql2

Changes:

 - moved into module java.sql.async (not reflected in the sandbox yet)
 - Removed references to java.sql
 - Implementation of SqlException and DataSourceFactory
 - New Transaction model
 - Flow.Processor for Operation submission and Row processing
 - Replace Future and CompletableFuture with CompletionStage
 - Replace initialValue and rowAggregator with collect(Collector)

Outstanding issues:

 - Implementation of DataSourceFactory needs work
 - Remove POJO support (open issue)
 - Remove @SqlArray and @SqlStruct (open-ish issue)
 - Improve JavaDoc on RowProcessorOperation
 - More JavaDoc
 - More text in package-info.java

Douglas