Refactor build system and UI

+ Install configs for Qt Designer plugins and Qtk application
+ Add Qtk plugin collection for Qt Designer
+ QtkWidget plugin
+ TreeView widget plugin
+ DebugConsole widget plugin
+ All widgets are fully integrated with Qt Designer
+ All widgets can be popped out or docked within the window
+ All widgets can be stacked to use tab view for side panels
+ All widgets can be toggled on/off through the view context menu
+ QtkWidget debug console
+ QtkWidget active scene TreeVew
+ QtkWidget dockable tool bar
+ Double-click an object name in the TreeView to focus camera
+ Separate libaray from widgets

There is still a lot to do here, but the major refactoring should be
done after this commit. Some of the new features were put together as
POC for working with the new UI. A few placeholder buttons were added
that have no functionality.

src/app/widgetplugin.h

@@ -0,0 +1,114 @@
+/*##############################################################################
+## Author: Shaun Reed                                                         ##
+## Legal: All Content (c) 2022 Shaun Reed, all rights reserved                ##
+## About: Generic Qt Designer widget plugin                                   ##
+##                                                                            ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com | GitHub: shaunrd0   ##
+################################################################################
+*/
+
+#ifndef QTK_WIDGETPLUGIN_H
+#define QTK_WIDGETPLUGIN_H
+
+#include <QDesignerCustomWidgetInterface>
+#include <QDesignerExportWidget>
+
+class QDESIGNER_WIDGET_EXPORT WidgetPlugin :
+    public QObject,
+    public QDesignerCustomWidgetInterface {
+    Q_OBJECT
+    Q_INTERFACES(QDesignerCustomWidgetInterface)
+
+    using Factory = std::function<QWidget *(QWidget *)>;
+
+  public:
+    WidgetPlugin(
+        QString group, QString class_name, QString include, Factory factory);
+
+    explicit WidgetPlugin(QObject * parent = nullptr) : QObject(parent) {}
+
+    ~WidgetPlugin() = default;
+
+  public:
+    /**
+     * @return The name of the group to which this widget belongs.
+     */
+    [[nodiscard]] QString group() const override;
+
+    /**
+     * Must return the _class name_ of the widget.
+     *
+     * @return The class name for the associated widget.
+     */
+    [[nodiscard]] QString name() const override;
+
+    /**
+     * If this path changes for a custom widget, it must be removed and added
+     * back in Qt Designer for the XML surrounding this value to be regenerated.
+     *
+     * See the `<customwidget>` XML in any `.ui` file using a custom widget.
+     *
+     * @return Path to the include file for UIC to use when generating code.
+     */
+    [[nodiscard]] QString includeFile() const override;
+
+    /**
+     * @param parent Parent widget to the new instance of this widget.
+     * @return A new instance of this custom widget.
+     */
+    QWidget * createWidget(QWidget * parent) override;
+
+    /**
+     * @return Short description used in Qt Designer tool tips.
+     */
+    [[nodiscard]] QString toolTip() const override;
+
+    /**
+     * @return Widget description used in `What's this?` within Qt Creator.
+     */
+    [[nodiscard]] QString whatsThis() const override;
+
+    /**
+     * @return Icon used to represent the widget in Qt Designer's GUI.
+     */
+    [[nodiscard]] QIcon icon() const override;
+
+    /**
+     * Whether or not this widget should act as a container for other widgets.
+     *
+     * @return True if this custom widget is meant to be a container.
+     */
+    [[nodiscard]] bool isContainer() const override;
+
+    /**
+     * @return True if this widget has been initialized.
+     */
+    [[nodiscard]] bool isInitialized() const override;
+
+    /**
+     * Initializes an instance of this custom widget.
+     * @param core
+     */
+    void initialize(QDesignerFormEditorInterface * core) override;
+
+    /**
+     * Default XML for an instance of this custom widget within a `.ui` file.
+     *
+     * Any property available for the widget in Qt Designer can be set using XML
+     * properties, as seen here with `toolTip` and `whatsThis`.
+     *
+     * @return XML inserted for each instance of this widget.
+     */
+    [[nodiscard]] QString domXml() const override;
+
+  private:
+    bool m_initialized = false;
+
+    QString m_group;
+    QString m_className;
+    QString m_objectName;
+    QString m_includeFile;
+    Factory m_factory;
+};
+
+#endif  // QTK_WIDGETPLUGIN_H