DERBY-5840: Clean up compiler warnings introduced by using Java 5 language features

Make the declared type of the lock groups HashMap<Lock, Lock> instead
of HashMap<Lock, Object>.

Stop suppressing unchecked conversion warnings in
PropertyConglomerate, and make all conversions checked.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1485609 13f79535-47bb-0310-9956-ffa450edef68