Update docs to refer to dropResets in rate options
Update docs to refer to dropResets in rate options

The docs currently don't list dropResets in the /api/query but it is one of the valid rate options.

https://github.com/OpenTSDB/opentsdb/blob/master/src/core/RateOptions.java#L88

The description for this option was grabbed directly from the source code which describes it.
manolama/opentsdb.net,OpenTSDB/opentsdb.net,OpenTSDB/opentsdb.net,OpenTSDB/opentsdb.net,manolama/opentsdb.net,manolama/opentsdb.net