Automation: AudacityCommand

This is a squash of 50 commits.

This merges the capabilities of BatchCommands and Effects using a new
AudacityCommand class.  AudacityCommand provides one function to specify the
parameters, and then we leverage that one function in automation, whether by chains,
mod-script-pipe or (future) Nyquist.

- Now have AudacityCommand which is using the same mechanism as Effect
- Has configurable parameters
- Has data-entry GUI (built using shuttle GUI)
- Registers with PluginManager.
- Menu commands now provided in chains, and to python batch.
   - Tested with Zoom Toggle.

- ShuttleParams now can set, get, set defaults, validate and specify
the parameters.
- Bugfix: Don't overwrite values with defaults first time out.
- Add DefineParams function for all built-in effects.
- Extend CommandContext to carry output channels for results.

We abuse EffectsManager.  It handles both Effects and
AudacityCommands now.  In time an Effect should become a special case of
AudacityCommand and we'll split and rename the EffectManager class.

- Don't use 'default' as a parameter name.
- Massive renaming for CommandDefinitionInterface
- EffectIdentInterface becomes EffectDefinitionInterface
- EffectAutomationParameters becomes CommandAutomationParameters
- PluginType is now a bit field.

This way we can search for related types at the same time.

- Most old batch commands made into AudacityCommands.
The ones that weren't are for a reason.  They are used by mod-script-pipe
to carry commands and responses across from a non-GUI thread to the GUI
thread.

- Major tidy up of ScreenshotCommand
- Reworking of SelectCommand
- GetPreferenceCommand and SetPreferenceCommand
- GetTrackInfo and SetTrackInfo
- GetInfoCommand
- Help, Open, Save, Import and Export commands.
- Removed obsolete commands ExecMenu, GetProjectInfo and SetProjectInfo
  which are now better handled by other commands.

- JSONify "GetInfo: Commands" output, i.e. commas in the right places.

- General work on better Doxygen.
    - Lyrics -> LyricsPanel
    - Meter -> MeterPanel
- Updated Linux makefile.
- Scripting commands added into Extra menu.
- Distinct names for previously duplicated find-clipping parameters.
- Fixed longstanding error with erroneous status field number which
  previously caused an ASSERT in debug.
- Sensible formatting of numbers in Chains, 0.1 not 0.1000000000137

src/commands/LoadCommands.h

@@ -0,0 +1,70 @@
+/**********************************************************************
+
+  Audacity: A Digital Audio Editor
+
+  LoadCommands.h
+
+  Dominic Mazzoni
+  James Crook
+
+**********************************************************************/
+
+#include "audacity/ModuleInterface.h"
+#include "audacity/EffectInterface.h"
+#include "audacity/PluginInterface.h"
+
+#include "AudacityCommand.h"
+#include "../MemoryX.h"
+
+///////////////////////////////////////////////////////////////////////////////
+//
+// BuiltinCommandsModule
+//
+///////////////////////////////////////////////////////////////////////////////
+
+class BuiltinCommandsModule final : public ModuleInterface
+{
+public:
+   BuiltinCommandsModule(ModuleManagerInterface *moduleManager, const wxString *path);
+   virtual ~BuiltinCommandsModule();
+
+   // IdentInterface implementation
+
+   wxString GetPath() override;
+   wxString GetSymbol() override;
+   wxString GetName() override;
+   wxString GetVendor() override;
+   wxString GetVersion() override;
+   wxString GetDescription() override;
+
+   // ModuleInterface implementation
+
+   bool Initialize() override;
+   void Terminate() override;
+
+   wxArrayString FileExtensions() override { return {}; }
+   wxString InstallPath() override { return {}; }
+
+   bool AutoRegisterPlugins(PluginManagerInterface & pm) override;
+   wxArrayString FindPluginPaths(PluginManagerInterface & pm) override;
+   unsigned DiscoverPluginsAtPath(
+      const wxString & path, wxString &errMsg,
+      const RegistrationCallback &callback)
+         override;
+
+   bool IsPluginValid(const wxString & path, bool bFast) override;
+
+   IdentInterface *CreateInstance(const wxString & path) override;
+   void DeleteInstance(IdentInterface *instance) override;
+
+private:
+   // BuiltinEffectModule implementation
+
+   std::unique_ptr<AudacityCommand> Instantiate(const wxString & path);
+
+private:
+   ModuleManagerInterface *mModMan;
+   wxString mPath;
+
+   wxArrayString mNames;
+};