API: Adding read, write latency histogram to column_family
API: Adding read, write latency histogram to column_family

This adds the latency histogram to the column_family swagger
definitions.
The definitions are based on the ColumnFamilyMetrics.
It adds the following commands:

get_read_latency_histogram
get_all_read_latency_histogram
get_write_latency_histogram
get_all_write_latency_histogram

Signed-off-by: Amnon Heiman <ed5fc74c4692051ad0b19749fd7cea6ec2d74b9e@cloudius-systems.com>

stamhe/scylla,asias/scylla,raphaelsc/scylla,duarten/scylla,dwdm/scylla,kangkot/scylla,justintung/scylla,victorbriz/scylla,glommer/scylla,aruanruan/scylla,scylladb/scylla,phonkee/scylla,dwdm/scylla,acbellini/scylla,scylladb/scylla,respu/scylla,gwicke/scylla,asias/scylla,victorbriz/scylla,wildinto/scylla,guiquanz/scylla,capturePointer/scylla,rluta/scylla,justintung/scylla,avikivity/scylla,duarten/scylla,scylladb/scylla,rentongzhang/scylla,kjniemi/scylla,rentongzhang/scylla,guiquanz/scylla,avikivity/scylla,eklitzke/scylla,duarten/scylla,acbellini/scylla,shaunstanislaus/scylla,kjniemi/scylla,aruanruan/scylla,gwicke/scylla,avikivity/scylla,shaunstanislaus/scylla,phonkee/scylla,glommer/scylla,senseb/scylla,eklitzke/scylla,gwicke/scylla,guiquanz/scylla,raphaelsc/scylla,linearregression/scylla,linearregression/scylla,kangkot/scylla,acbellini/scylla,stamhe/scylla,rentongzhang/scylla,capturePointer/scylla,asias/scylla,dwdm/scylla,raphaelsc/scylla,senseb/scylla,bowlofstew/scylla,senseb/scylla,phonkee/scylla,tempbottle/scylla,glommer/scylla,wildinto/scylla,linearregression/scylla,bowlofstew/scylla,tempbottle/scylla,bowlofstew/scylla,tempbottle/scylla,rluta/scylla,justintung/scylla,stamhe/scylla,aruanruan/scylla,eklitzke/scylla,rluta/scylla,respu/scylla,wildinto/scylla,capturePointer/scylla,shaunstanislaus/scylla,kangkot/scylla,kjniemi/scylla,scylladb/scylla,victorbriz/scylla,respu/scylla