Handle decimation levels changing

Timofey asked:

If we change levels and new intervals are not multiples of old intervals, decimation will erase all the stats that was collected before the levels change. Is that correct?
Example:

  [{level1, 1d, 61}] -> [{level1, 1d, 67}]

Steve Watanabe

Yes, if new decimation levels are not aligned with the prior ones then older data may be lost. e.g. if the existing stats were decimated to 1 stat per every 7 minutes and it's changed to 1 every 9 minutes then the alignment is off except every 63 minutes.

Timofey Barmin
I guess we should prevent stats disappearance