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/AppCommandEvent.h

@@ -22,13 +22,13 @@
 
 DECLARE_EXPORTED_EVENT_TYPE(AUDACITY_DLL_API, wxEVT_APP_COMMAND_RECEIVED, -1);
 
-class Command;
-using CommandHolder = std::shared_ptr<Command>;
+class OldStyleCommand;
+using OldStyleCommandPointer = std::shared_ptr<OldStyleCommand>;
 
 class AppCommandEvent final : public wxCommandEvent
 {
 private:
-   CommandHolder mCommand;
+   OldStyleCommandPointer mCommand;
 
 public:
    AppCommandEvent(wxEventType commandType = wxEVT_APP_COMMAND_RECEIVED, int id = 0);
@@ -37,8 +37,8 @@ public:
    ~AppCommandEvent();
 
    wxEvent *Clone() const override;
-   void SetCommand(const CommandHolder &cmd);
-   CommandHolder GetCommand();
+   void SetCommand(const OldStyleCommandPointer &cmd);
+   OldStyleCommandPointer GetCommand();
 
 private:
    DECLARE_DYNAMIC_CLASS(AppCommandEvent)