anchor.diff:  
   For every package/version in the packages definition, there is a unique `SolrResourceLoader` instance. This is a child of the `CoreContainer` resource loader.
   
  +=== `packages.json`
  +
  +The package configurations live in a file called /packages.json in Zookeeper. At any given moment we can have multiple versions of a given package in the package configuration. The system will always use the latest version . Versions are sorted by their numeric value and the biggest is the latest.
  +
  +*example:*
  +
  +[source, json]
  +----
  +{
  + "packages" : {
  +   "mypkg" : {
  +     "name": "mypkg",
  +     "versions": [
  +       {"version" : "0.1",
  +       "files" : ["/path/to/myplugin/1.1/plugin.jar"]
  +       },
  +       {"version" :  "0.2",
  +       "files" : ["/path/to/myplugin/1.0/plugin.jar"]
  +       }]}},
  +
  +----
  +
   === API end points
   
   * `GET /api/cluster/package` Get the list of packages
  
positive.code: 
  A Package in Solr may contain one or more .jar files and any no:of plugins.
  
  
  == A Plugin
  
  
negative.code: ----
  
  == Package Store
  Package store is a distributed file store which can store arbitrary files in the file system.
  
  * This is a fully replicated file system based repository.
  * It lives at <solr.home>/filestore on each Solr node
  * Every entry  is a file + metadata. The metadata is named .<filename>.json
  * The metadata file contains the sha256, signatures of the file
  * Users can’t create files starting with period (.)
  * It is agnostic of content type of files. You may store jars as well as other files.
  
  === How does the Package Store work?
  When a file is uploaded to the PackageStore ,
  
  * It’s saved to the local file system
  * It’s saved along with the metadata. The metadata file stores the sha512 and signatures of the jar files too.
  * Every live node in the cluster is asked to download it as well
  
  === Package Store APIs
  
  