Compile-fix for move of FCPPluginClient to different package

Was done on fred branch plugin-fcp-rewrite-purge-db4o recently.
It was moved from freenet.node.fcp to freenet.clients.fcp
Compile-fix for removed callback TransferThread.onMajorProgress()

Was removed from fred in commit
93c9564237a890f4871f0a3909f3276a72b3d769.
The implementations in WOT were all empty/unused, so this commit removes
them without replacement.
Compile-fix for HighLevelSimpleClient.fetch() signature change

The RequestClient parameter was removed in commit
ce57959a614e5767bf497f69e6b8608bb2707fdc:

-	public ClientGetter fetch(FreenetURI uri, long maxSize,
RequestClient
context, ClientGetCallback callback, FetchContext fctx, short
priorityClass) throws FetchException;
+	public ClientGetter fetch(FreenetURI uri, long maxSize,
ClientGetCallback callback, FetchContext fctx, short priorityClass)
throws FetchException;

It is obtained from a callback instead now, which this commit adds.