Save and Load context state data

• LLM Farm is now able to save a session to a special file and load it later to resume dialog with LLM.
• This option is enabled by default.
• If you want to disable the save option, you can do so in the "Advanced" section of the chat settings.
• If you want to reset the current state of the chat, you can use the "Reload dialog" and "Clear chat" buttons.