CAY-1890 Remove Cayenne-level buffering when retrieving LOBs

git-svn-id: https://svn.apache.org/repos/asf/cayenne/main/trunk@1547890 13f79535-47bb-0310-9956-ffa450edef68
CAY-1890 Remove Cayenne-level buffering when retrieving LOBs

also switching DerbyAdapter to use CLOBs

git-svn-id: https://svn.apache.org/repos/asf/cayenne/main/trunk@1547891 13f79535-47bb-0310-9956-ffa450edef68
CAY-1890 Remove Cayenne-level buffering when retrieving LOBs

same for BLOBs

git-svn-id: https://svn.apache.org/repos/asf/cayenne/main/trunk@1547892 13f79535-47bb-0310-9956-ffa450edef68