Class AbstractEditor

Still required is

 1. a custom `static editorOf(p, c, o)`-method, to register on a schema
 2. an `update(event)`-method to respond to changes

Convenience methods are

 - `getData()` to fetch the associated data of the current _pointer_
 - `setData(newValue)` to update the associated data of the current _pointer_
 - `getSchema()` returning the json-schema of the current _pointer_
 - `getErrors()` returning a list of current errors
 - `getElement()` gives you the root dom-node for this editor (aka render target)
 - `focus()` and `blur()` to manage the selection state of the current input (requires correct placement of _id_)

param

pointer referencing the current data and schema

param

editron instance

param

resolved options object