Rollup should no longer be a continuous running job. Instead, it should be an action that can be triggered on ILM-managed indices. The action should iterate over all grouping tuples (dimensions) and calculate aggregate metrics (min/max/avg/value_count) generating one document per grouping tuple (dimension).

In the context of this issue we should implement the following:

• Implement a "grouping tuple" field type to generate the tuple at index time for the document.
• Implement a "rollup metric" field type to store aggregation results (min/max/count/avg etc). This metric should provide the correct information to requesting aggregator (e.g. avg agg on rollup_metric will internally fetch sum + count)
• Store document count somewhere on the document (docvalue field?)
• Create an ILM rollup action