Commands

- New 'exec' command that runs external programs, implemented by
  CmdExec.
- Restructured code so that only Commands implements ::read_only
  and ::displays_id methods, while derived objects simply set flags.
- Corrected column alignment in summary report.

src/commands/CmdLogo.cpp

@@ -25,7 +25,7 @@
 //
 ////////////////////////////////////////////////////////////////////////////////
 
-#include <iostream>
+#include <iostream> // TODO Remove.
 #include <CmdLogo.h>
 #include <Context.h>
 #include <text.h>
@@ -35,21 +35,12 @@ extern Context context;
 ////////////////////////////////////////////////////////////////////////////////
 CmdLogo::CmdLogo ()
 {
+  _read_only   = true;
+  _displays_id = false;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
-CmdLogo::~CmdLogo ()
-{
-}
-
-////////////////////////////////////////////////////////////////////////////////
-bool CmdLogo::read_only () const
-{
-  return true;
-}
-
-////////////////////////////////////////////////////////////////////////////////
-bool CmdLogo::implements (const std::string& command_line) const
+bool CmdLogo::implements (const std::string& command_line)
 {
   // TODO Upgrade to a parsed value.
   if (command_line.find ("_logo") != std::string::npos)