Added an execute() method to context to catch unhandled commands

lib/Shell.php

@@ -223,6 +223,12 @@ class Shell
             }
             return;
         }
+
+        // Call 'execute' on the current context
+        if ($this->context->execute($command, ...$args)) {
+            return;
+        }
+
         // Throw error if the command could not be found
         throw new Exception\BadCommandException("Command {$command} not found");
     }