Implement set-policy and remove-policy APIs

curl -H 'Content-type:application/json' -d '{
 "set-cluster-preferences":[
        {"minimize": "replicas", "precision": 3},
        {"maximize": "freedisk","precision": 100},
        {"minimize": "cpu","precision": 10}]
  }
  "set-cluster-policy": [
      {"cores":"<10", "node":"#ANY"},
      {"replica":"<2", "shard": "#EACH", "node": "#ANY"},
      {"nodeRole":"!overseer", "replica":"#ANY"}
    ],
 "set-policy":{
     "mypolicy":  [
      {"cores":"<10", "node":"#ANY"}    
    ] }
}' http://localhost:8983/solr/admin/autoscaling

curl -H 'Content-type:application/json' -d '{
  "remove-policy": "policy1"
}' http://localhost:8983/solr/admin/autoscaling