Add FieldlinesState class files

modules/fieldlinessequence/rendering/renderablefieldlinessequence.h

@@ -27,6 +27,8 @@
 
 #include <openspace/rendering/renderable.h>
 
+#include <modules/fieldlinessequence/util/fieldlinesstate.h>
+
 namespace openspace {
 
 class RenderableFieldlinesSequence : public Renderable {
@@ -43,6 +45,8 @@ public:
     void update(const UpdateData& data) override;
 private:
     std::string _loggerCat = "RenderableFieldlinesSequence";
+
+    std::vector<FieldlinesState> _states;
 };
 
 } // namespace openspace