Adding capability to delete resources via label selector

@smarterclayton, @bgrant0607  @derekwaynecarr Thanks to have a look when you have time

See #2438 for motivation.
Finally: I'm going to modify the server to take the label selector. This will simplify the code (removing the need of the tmp struct). And I'll assume  that the list of resources (to be verified by server) is going to be separated by blank.