Add SkipAnalyzer.

This is WIP: The test case would require a new pcap or the possibility
to overwrite analyzer mappings. The CustomEncapsulationSkip method and
the corresponding options need to be removed.

src/packet_analysis/Dispatcher.cc

@@ -48,6 +48,7 @@ bool Dispatcher::Register(uint32_t identifier, AnalyzerPtr analyzer)
 		}
 
 	int64_t index = identifier - lowest_identifier;
+	//TODO: Allow to overwrite mappings?
 	if ( table[index] == nullptr )
 		{
 		table[index] = analyzer;