reminder messages, auto-summarization, and a bunch of other stuff

• added "reminder message" in character creator - basically completely stops gpt-3.5-turbo from breaking character ("as an ai language model...", or forgetting important context) in my initial tests! this could be implemented pretty easily with a custom code snippet, but it definitely seems useful enough to be a built in feature
• old messages are now summarized to give the AI a longer memory (slows responses a bit - can be disabled in character advanced options)
• /sys <message> command for creating system messages
• custom code can now create system messages
• /ai command for prompting another ai message
• /ai <message> command for speaking as the ai
• search threads
• added "starter characters" section
• initial system set up for seeing "behind the scenes" (logs/etc.) - click the "summarizing (N)" to see summaries. more/better logs to come later (open an issue if there's some particular data that you want to see)
• fixed this bug
• some minor ergonomics/cosmetic fixes