headers MAINTENANCE headers/include cleanup

- add missing extern "C" in some of the public headers for use in C++
- includes cleanup and fix ordering
diff --git a/src/libyang.h b/src/libyang.h
index 72486e3..18c5de5 100644
--- a/src/libyang.h
+++ b/src/libyang.h
@@ -21,6 +21,8 @@
 extern "C" {
 #endif
 
+#include "context.h"
+#include "dict.h"
 #include "log.h"
 #include "parser.h"
 #include "parser_schema.h"
@@ -29,16 +31,9 @@
 #include "printer_data.h"
 #include "printer_schema.h"
 #include "set.h"
-#include "dict.h"
-#include "context.h"
 #include "tree.h"
 #include "tree_data.h"
 #include "tree_schema.h"
-#include "printer.h"
-#include "printer_data.h"
-#include "printer_schema.h"
-#include "printer_data.h"
-#include "plugins_types.h"
 
 /**
  * @mainpage About