Expose dataflow API in a single header file.

Now end users only have to #include<pls/dataflow/dataflow.h> to use all parts of the API. We split dataflow out from the general algorithms header, as it is a rather big API and could bloat the users namespace/includes.

lib/pls/include/pls/dataflow/dataflow.h

@@ -2,8 +2,35 @@
 #ifndef PLS_DATAFLOW_DATAFLOW_H_
 #define PLS_DATAFLOW_DATAFLOW_H_
 
-#include "graph.h"
-#include "pls/dataflow/internal/inputs.h"
-#include "pls/dataflow/internal/outputs.h"
+#include "internal/graph.h"
+#include "internal/function_node.h"
+#include "internal/merge_node.h"
+#include "internal/switch_node.h"
+#include "internal/split_node.h"
+
+#include "internal/inputs.h"
+#include "internal/outputs.h"
+
+namespace pls {
+namespace dataflow {
+
+template<typename INS, typename OUTS>
+using graph = internal::graph<INS, OUTS>;
+template<typename INS, typename OUTS, typename F>
+using function_node = internal::function_node<INS, OUTS, F>;
+template<typename I>
+using merge_node = internal::merge_node<I>;
+template<typename I>
+using switch_node = internal::switch_node<I>;
+template<typename I>
+using split_node = internal::split_node<I>;
+
+template<typename ...I>
+using inputs = internal::inputs<I...>;
+template<typename ...O>
+using outputs = internal::outputs<O...>;
+
+}
+}
 
 #endif //PLS_DATAFLOW_DATAFLOW_H_