anchor.diff:  
   * `%` : A certain percentage of the value. This is supported by the following attributes
   ** `replica`
  +** `freedisk`
   
   === Examples of Policy Rules
   
  
positive.code: 
  [source,json]
  {"replica": 0, "freedisk": "<500"}
  
  ==== Try to Place Replicas Based on Free Disk
  Place all replicas in nodes with freedisk more than 500GB when possible. Here we use the strict keyword to signal that this rule is to be honored on a best effort basis.
  
negative.code: * a number with a decimal value . e.g: "`1.66`" . This means both 1 and 2 are acceptable values but the system would prefer `2`
  * a number range. Such as `"3-5"` . This means `3,4,5` are acceptable values
  * a percentage value . e.g: `33%` . This is computed to a decimal value at runtime
  * `#EQUAL` : means divide it equally among all the nodes qualifying a certain property
  
  `strict`::
  An optional boolean value. The default is `true`. If true, the rule must be satisfied. If false, Solr tries to satisfy the rule on a best effort basis but if no node can satisfy the rule then any node may be chosen.
  