This patch updates the GUI::SearchTab to use the Gnutella::LocalPeer as facade for searching.

This was done to hide the details of the Gnutella implementation from the higher layers.
We should proceed by adding one more abstraction level, as already described in the Calitko Architecture document. This would be the SearchService which will know about all searchable networks and will manage searches and search results. Generally, it should manage searches independent from the network. We should pull as much of the management as possible up in this abstraction to avoid implementing the same stuff all over again for each network. Peter will be back with more information concerning the SearchService later.