Ephemeral self-notes

[Zomis]

Some games could benefit from a note system where you could make notes to yourself (could be useful for all games to note down what your plans are).

Alchemists (see #136) would benefit extra much from this as it has a "deduction grid" where players can note down what they know (which ingredients can or cannot be what alchemical).

The history of these notes do not need to be stored in the database, as that could lead to a massive explosion of database items. So they should probably not be considered as regular actions. It could also need some protection against auto-clickers and such. Only allow each player a limited amount of updates per second, with a maximum saved amount as well. Use simple rate limiter algorithm.