feat: Implement OFX plugin support infrastructure

This commit adds comprehensive support for OFX plugins in Olive, including:

- Add plugin node infrastructure with getPlugin() method
- Implement OliveHost for managing OFX plugin instances
- Create OliveInstance to handle plugin parameter and timeline interactions
- Add OliveClip implementation for plugin clip handling
- Implement region of definition (RoD) and region of interest (RoI) functionality
- Add interactive mode support in Current class
- Integrate plugin rendering into RenderProcessor
- Fix include dependencies and remove unused OlivePlugin.cpp reference

app/common/Current.h

@@ -51,6 +51,10 @@ public:
 	{
 		currentAudioParams_ = params;
 	}
+	bool interactive()
+	{
+		return true;
+	}
 private:
 	static Current current;
 	olive::VideoParams currentVideoParams_;