CIDR to ip_range

[eskibars]

Describe the feature:
Currently the ip_range type accepts the standard range notation (e.g. gte, lte). However, IP ranges are fairly commonly defined by a CIDR. It adds some complexity to the mapping internally, but in order to avoid having to do the conversion externally when the source data may come directly from e.g. a network switch and also to cut down on the overall size of _source, it may be nice to support the implicit conversion.

[s1monw]

we discussed it in fixit firday and we are convinced we should do this. Not sure about the priority. I am labeling it adopt me.