more info on liveliness errors

[xaviergonz]

Fixes #1142

Gives additional info on liveliness errors:

• the path that the node used to have when it was last seen alive
• the subpath being accessed/written to (if any)
• the action name and path the error happened inside (if any)

Examples

const todo = root.todo
root.todo = undefined // todo becomes dead

todo.fn()
"You are trying to read or write to an object that is no longer part of a state tree.
(Object type: 'Todo', Path upon death: '/todo', Subpath: '', Action: '/todo.fn()').
Either detach nodes first, or don't use objects after removing / replacing them in the tree."

todo.title
"You are trying to read or write to an object that is no longer part of a state tree.
(Object type: 'Todo', Path upon death: '/todo', Subpath: 'title', Action: '').
Either detach nodes first, or don't use objects after removing / replacing them in the tree."