Added a replaceNoSync() method to DBObjectTable

This method is intended to support making fieldAry
private and final in DBObject, by getting rid of
the old DBObject.updateBaseRef() method, in favor
of an optimized copy constructor.

This will help us make references to read-only DBObject
truly immutable, even during schema editing.
Fixed an NPE that I just introduced in DateDBField.value().
Microcleanups in DBObject.java
Oops!  We need to set objectBase in the DBObject receive constructor before calling receive()
Fixed InvidDBField.getRemoteLabel() when the target Invid isn't registered in the system
Fixed DBObject.appendObjectInfo() when it's called before all Invid targets are loaded
Fixed SyncRunner initialization when the Sync Channel Fields field is not present in the Sync Channel object
Small cleanups in server.  Mostly comments.