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

lib/Context.php

@@ -146,6 +146,23 @@ class Context
         return array_key_exists('global', $info);
     }
 
+    /**
+     * Catch-all handler for commands not defined in context, globally or builtin.
+     * Override this function and return true if the command is handled ok.
+     *
+     * @param string $command The command to execute
+     * @param string[] $args The arguments to the command
+     * @return bool True if the command was handled
+     */
+    public function execute($command, ...$args)
+    {
+        return false;
+    }
+
+    /**
+     * Get the name of the context
+     *
+     */
     public function getName()
     {
         return $this->name;