RHQ REST api: added support for Group Definitions

I've just added some support for GroupDefinitions (aka "DynaGroups") to RHQ.

The following shows some examples:

List all definitions:

$ curl -i --user rhqadmin:rhqadmin http://localhost:7080/rest/1/group/definitions
[{"name":"group1",
  "id":10001,
  "description":"just some random test",
  "expression":["groupby resource.type.plugin","groupby resource.type.name"],
   "recursive":false,
   "recalcInterval":180000,
   "generatedGroupIds":[10082,10091]},
  {"name":"platforms",
   "id":10002,
   "description":"",
   "expression":["resource.type.category = PLATFORM","groupby resource.name"],
   "recursive":false,
   "recalcInterval":0,
   "generatedGroupIds":[10152]}
]

Get a single definition by id:

$ curl -i --user rhqadmin:rhqadmin http://localhost:7080/rest/1/group/definition/10002
{"name":"platforms",
 "id":10002,
 "description":"",
 "expression":["resource.type.category = PLATFORM","groupby resource.name"],
 "recursive":false,
 "recalcInterval":0,
 "generatedGroupIds":[10152]
}

You see in the above examples that the actual expression is encoded as a list with each line being an item in the list. The recalculation interval needs to be given in milliseconds.

Delete a definition (by id):

$ curl -i --user rhqadmin:rhqadmin http://localhost:7080/rest/1/group/definition/10031 -X DELETE

Create a new definition:

$ curl -i --user rhqadmin:rhqadmin http://localhost:7080/rest/1/group/definitions \
   -HContent-Type:application/json -HAccept:application/json -X POST \
   -d '{"name":"test1","description":"Hello","expression":["groupBy resource.name"]}'
HTTP/1.1 201 Created
Location: http://localhost:7080/rest/1/group/definition/10041

For creation a name is required. The location of the created group definition is returned in the header of the response.

And finally to update a definition:

curl -i --user rhqadmin:rhqadmin http://localhost:7080/rest/1/group/definition/10041?recalculate=true \
   -HContent-Type:application/json -HAccept:application/json -X PUT  \
   -d '{"name":"test4","description":"Hello","expression":["groupBy resource.name"]}'

By passing the query-param recalculate=true we can trigger a re-calculation of the groups defined by this group definition.