Schema: add 'starred' state to the state table
Scheme: Add error state to state table
API: rename mark-read parameter to change-state

* change-state now takes a string name of the new state
* previously, mark-read accepted a boolean (read/unread)
JS: update mark_read and mark_unread methods to use new change-state api call
JS: add new 'star' method to api
Frontend: Add empty star icon next to each item

* will become control/indicator for item starred status
API: fix variable name, state is now stored in $new_state, not $value
Frontend: update state dependend code to account for new starred state
Frontend: update star icon based on item state
Frontend: add click handler to star icon

* if item is unread  => move to starred state
* if item is read    => move to starred state
* if item is starred => move to read state
Frontend: split star toggle code into separate method
Frontend: add keyboard shortcut (s) to toggle the item starred state
Spec bumps: New 'starred' item state