Index patterns - simplify relationship between IndexPattern class, IIndexPattern, and IndexPatternSpec #78378
Description
While the main api methods IndexPatterns has been refactored, the object structure needs a similar simplification which mainly affects functions that take IndexPattern instances as arguments. IIndexPattern provides a means of accepting either an IndexPattern instance or a plain javascript object. It would be better to use the IndexPatternSpec more widely since its easy to configure and can be generated by an IndexPattern instance.