nodes: use defined categories rather than arbitrary string based

app/node/input/time/timeinput.cpp

@@ -41,9 +41,9 @@ QString TimeInput::id() const
   return QStringLiteral("org.olivevideoeditor.Olive.time");
 }
 
-QString TimeInput::Category() const
+QList<Node::CategoryID> TimeInput::Category() const
 {
-  return tr("Input");
+  return {kCategoryInput};
 }
 
 QString TimeInput::Description() const

app/node/input/time/timeinput.h

@@ -35,7 +35,7 @@ public:
 
   virtual QString Name() const override;
   virtual QString id() const override;
-  virtual QString Category() const override;
+  virtual QList<CategoryID> Category() const override;
   virtual QString Description() const override;
 
   virtual NodeValueTable Value(NodeValueDatabase& value) const override;