* Doc: logic mixin, drop underscore, clarify
conventionally, we added a leading underscore to logic mixins' function
names. This is noisy in the warning section of IDEs. Leading underscores
should only be used for private/protected functions.
In addition, the use of self.world and/or requirement to (no) pass in stuff
was not made clear earlier.
* SoE: fix _ warnings for logic mixin
* Add stone theme
* Fix h2 color, change rogue-legacy to stone theme (approved by Phar)
* Add stone theme preview to world api.md
* Different stone theme preview to match other images