config: allow configuring partitions

This just allows creating empty partitions.  More features to come.

src/Main.cxx

@@ -410,6 +410,15 @@ MainConfigured(const CommandLineOptions &options,
 		partition.UpdateEffectiveReplayGainMode();
 	}
 
+	raw_config.WithEach(ConfigBlockOption::PARTITION, [&](const auto &block){
+		const char *name = block.GetBlockValue("name");
+		if (name == nullptr)
+			throw std::runtime_error("Missing 'name'");
+
+		instance.partitions.emplace_back(instance, name,
+						 partition_config);
+	});
+
 	client_manager_init(raw_config);
 	const ScopeInputPluginsInit input_plugins_init(raw_config,
 						       instance.io_thread.GetEventLoop());

src/config/Option.hxx

@@ -97,6 +97,7 @@ enum class ConfigBlockOption {
 	AUDIO_FILTER,
 	DATABASE,
 	NEIGHBORS,
+	PARTITION,
 	MAX
 };
 

src/config/Templates.cxx

@@ -96,6 +96,7 @@ const ConfigTemplate config_block_templates[] = {
 	{ "filter", true },
 	{ "database" },
 	{ "neighbors", true },
+	{ "partition", true },
 };
 
 static constexpr unsigned n_config_block_templates =