The fabled realtime effects...

I've made it where you can enable and disable via experimentals:

EXPERIMENTAL_REALTIME_EFFECTS
EXPERIMENTAL_EFFECTS_RACK

You will notice that, as of now, the only effects currently set up for
realtime are VSTs.  Now that this is in, I will start converting the
rest.

As I start to convert the effects, the astute of you may notice that
they no longer directly access tracks or any "internal" Audacity
objects.  This isolates the effects from changes in Audacity and makes
it much easier to add new ones.

Anyway, all 3 platforms can now display VST effects in graphical mode.
Yes, that means Linux too.  There are quite a few VSTs for Linux if
you search for them.

The so-called "rack" definitely needs some discussion, work, and attention
from someone much better at graphics than me.  I'm not really sure it should
stay in as-is.  I'd originally planned for it to be simply a utility window
where you can store your (preconfigured) favorite effects.  It should probably
revert back to that idea.

You may notice that this DOES include the API work I did.  The realtime effects
were too tied to it and I didn't want to redo the whole thing.  As I mentioned
elsewhere, the API stuff may or may not be very future proof.

So, let the critter complaints commence.  I absolute KNOW there will be some.
(I know I'll be hearing from the Linux peeps pretty darn quickly.  ;-))

src/AudacityApp.cpp

@@ -68,12 +68,12 @@ It handles initialization and termination by subclassing wxApp.
 #include "commands/AppCommandEvent.h"
 #include "effects/LoadEffects.h"
 #include "effects/Contrast.h"
-#include "effects/VST/VSTEffect.h"
 #include "widgets/ASlider.h"
 #include "FFmpeg.h"
 #include "Internat.h"
 #include "LangChoice.h"
 #include "Languages.h"
+#include "PluginManager.h"
 #include "Prefs.h"
 #include "Project.h"
 #include "Screenshot.h"
@@ -95,7 +95,7 @@ It handles initialization and termination by subclassing wxApp.
 //temporarilly commented out till it is added to all projects
 //#include "Profiler.h"
 
-#include "LoadModules.h"
+#include "ModuleManager.h"
 
 #include "import/Import.h"
 
@@ -274,7 +274,7 @@ void QuitAudacity(bool bForce)
 
    LWSlider::DeleteSharedTipPanel();
 
-   ModuleManager::Dispatch(AppQuiting);
+   ModuleManager::Get().Dispatch(AppQuiting);
 
    if (gParentFrame)
       gParentFrame->Destroy();
@@ -1008,6 +1008,7 @@ int AudacityApp::FilterEvent(wxEvent & event)
    return -1;
 }
 #endif
+#include "effects/VST/VSTEffect.h"
 
 // The `main program' equivalent, creating the windows and returning the
 // main frame
@@ -1042,16 +1043,6 @@ bool AudacityApp::OnInit()
    wxTheApp->SetVendorName(vendorName);
    wxTheApp->SetAppName(appName);
 
-#ifdef USE_VST // if no VST support, answer is always no
-   // Have we been started to check a plugin?
-   if (argc == 3 && wxStrcmp(argv[1], VSTCMDKEY) == 0) {
-      wxHandleFatalExceptions();
-
-      VSTEffect::Check(argv[2]);
-      return false;
-   }
-#endif
-
    // Unused strings that we want to be translated, even though
    // we're not using them yet...
    wxString future1 = _("Master Gain Control");
@@ -1183,9 +1174,12 @@ bool AudacityApp::OnInit()
 
    // Initialize the CommandHandler
    InitCommandHandler();
-   // Initialize the ModuleManager, including loading found modules
-   ModuleManager::Initialize(*mCmdHandler);
 
+   // Initialize the PluginManager
+   PluginManager::Get().Initialize();
+
+   // Initialize the ModuleManager, including loading found modules
+   ModuleManager::Get().Initialize(*mCmdHandler);
 
 #if !wxCHECK_VERSION(3, 0, 0)
    FinishInits();
@@ -1248,7 +1242,6 @@ void AudacityApp::FinishInits()
 
    LoadEffects();
 
-
 #ifdef __WXMAC__
 
    // On the Mac, users don't expect a program to quit when you close the last window.
@@ -1310,7 +1303,7 @@ void AudacityApp::FinishInits()
    FFmpegStartup();
    #endif
 
-   mImporter = new Importer;
+   Importer::Get().Initialize();
 
    //
    // Auto-recovery
@@ -1474,7 +1467,7 @@ void AudacityApp::FinishInits()
 
    gInited = true;
 
-   ModuleManager::Dispatch(AppInitialized);
+   ModuleManager::Get().Dispatch(AppInitialized);
 
    mWindowRectAlreadySaved = FALSE;
 }
@@ -1823,8 +1816,7 @@ int AudacityApp::OnExit()
    delete mIPCServ;
 #endif
 
-   if (mImporter)
-      delete mImporter;
+   Importer::Get().Terminate();
 
    if(gPrefs)
    {
@@ -1856,6 +1848,9 @@ int AudacityApp::OnExit()
 
    DeinitAudioIO();
 
+   // Terminate the PluginManager (must be done before deleting the locale)
+   PluginManager::Get().Terminate();
+
    if (mLocale)
       delete mLocale;
    delete mChecker;