storage_proxy: Reconciliation. The beginning
storage_proxy: Reconciliation. The beginning

The patch introduces reconciliation code. The same code suppose to be
working for both range and single key queries. Handling of raw_limit,
short reads and read repairs is still very much missing.

--
v1->v2:
  - call live_row_count() only once.

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