Argument Parsing

- Obsoleted Command::exectute  'commandLine' argument.  It is worse
  than unnecessary, it is an uncategorized raw argument string, which
  is only really useful for the 'execute' command, which itself now
  calls Arguments::combine to reconstruct the command line string.

src/commands/CmdDiagnostics.cpp

@@ -63,7 +63,7 @@ CmdDiagnostics::CmdDiagnostics ()
 //
 // Although this will change over time, initially this command will answer the
 // kind of questions we always have to ask whenever something is wrong.
-int CmdDiagnostics::execute (const std::string&, std::string& output)
+int CmdDiagnostics::execute (std::string& output)
 {
   Color bold ("bold");