Fixed missing editor related methods for SlickGrid Definitions

Hello,

I found the SlickGrid definition was missing some methods required for implementation of editors, so I went ahead an added them:

- missing EditorFactory properties from https://github.com/mleibman/SlickGrid/wiki/Writing-custom-cell-editors
- Column.validator required by editor implementations: https://github.com/mleibman/SlickGrid/blob/master/slick.editors.js
- Types of DataView-Methods according to source: https://github.com/mleibman/SlickGrid/blob/master/slick.dataview.js