Fix onGeneratedMetadata() missing supertype definition

- Compiler error would be "The method onGeneratedMetadata(Bucket,
BaseClientPutter, ObjectContainer) of type * must override or implement
a supertype"
- This branch shall fix compiling against the removal of db4o, and
ObjectContainer is a db4o type, so the natural solution is to remove
that parameter.
Compile-fix for getCHKOnly begin moved to InsertContext

- Error would be similar to "The method insert(InsertBlock, String,
boolean, InsertContext, ClientPutCallback, short) in the type
HighLevelSimpleClient is not applicable for the arguments (InsertBlock,
boolean, null, boolean, InsertContext, IdentityInserter, short)"
- There is a fred commit which solely removed the getCHKOnly boolean
parameter and moved it to FetchContext,
(https://github.com/freenet/fred/commit/6596c3e238340ce19a34f9e32611862c8f2a4390)
so the proper fix is to use the function without that parameter
- A FIXME is added to check whether false is the default, which I
suspect. I will do this with the debugger once everything compiles.