* Store,State: Add update param to all store.XXXStore.XXXSet methods
* State: add paginating Messages
* Store: Fix test error
* store: merge shouldPrependMessage and shouldAppendMessage into single messageInsertPosition
This commit refactors the Store interface in State into smaller
interfaces in package store. These interfaces are combined into one
structure called a "Cabinet". The default implementation of those
interfaces have been rewritten in package defaultstore, while the old
no-op implementation stays with the store package.
This commit also omitted several state handlers for user events, as it
is unclear what they are actually structured like.
diamondburned