another try at a resource buf api

  * it is now templated to reduce casting
  * change all uses of ResourceBuff in cyclus agents to ResBuf
  * use C INFINITY macro instead of custom kInfinity constant
  * PushAll-> Push
  * PopQty -> Pop and it now returns the resources squashed
  * added PopRes and PopNRes methods
  * pending deprecation warn on resourcebuff
  * added a Peek method
added example to doc comments