Kernel: Add partial support for shell

We don't handle arrow keys, and the tty does not know how to clear
the screeen :D

kernel/include/kernel/Shell.h

@@ -19,10 +19,9 @@ namespace Kernel
 		void rerender_buffer() const;
 		BAN::Vector<BAN::String> parse_arguments(BAN::StringView) const;
 		BAN::ErrorOr<void> process_command(const BAN::Vector<BAN::String>&);
-		void key_event_callback(Input::KeyEvent);
 		BAN::ErrorOr<void> update_prompt();
 
-	private:		
+	private:
 		BAN::Vector<BAN::String>	m_old_buffer;
 		BAN::Vector<BAN::String>	m_buffer;
 		BAN::String					m_prompt_string;

kernel/include/kernel/Terminal/TTY.h

@@ -39,6 +39,7 @@ namespace Kernel
 		void render_from_buffer(uint32_t x, uint32_t y);
 
 		void on_key(Input::KeyEvent);
+		void do_backspace();
 
 	private:
 		enum class State