Harmlessly qualify classes as final (or explicitly comment not)...

... Should have no effect on generated code, except perhaps some slight faster
virtual function calls.  Mostly useful as documentation of design intent.

Tried to mark every one of our classes that inherits from another, or is a
base for others, or has abstract virtual functions, and a few others besides.

src/commands/Command.h

@@ -57,7 +57,7 @@ public:
 };
 
 // Interface
-class Command
+class Command /* not final */
 {
 public:
    virtual void Progress(double completed) = 0;
@@ -71,7 +71,7 @@ public:
 };
 
 // Command which wraps another command
-class DecoratedCommand : public Command
+class DecoratedCommand /* not final */ : public Command
 {
 protected:
    Command *mCommand;
@@ -94,7 +94,7 @@ public:
 
 // Decorator command that performs the given command and then outputs a status
 // message according to the result
-class ApplyAndSendResponse : public DecoratedCommand
+class ApplyAndSendResponse final : public DecoratedCommand
 {
 public:
    ApplyAndSendResponse(Command *cmd)
@@ -104,7 +104,7 @@ public:
    virtual bool Apply(CommandExecutionContext context);
 };
 
-class CommandImplementation : public Command
+class CommandImplementation /* not final */ : public Command
 {
 private:
    CommandType &mType;