Add host resources

Retrieve host resources

The state machine calculates the host resources on every update. In the beginning when there is no information about the resources and the containers, the resources (cpu and memory) are both set to -1, so that the scheduling algorithm won't choose them. On every (re)connect of the agent the host resources are recalculated and when connection is lost they are set again to -1.

@bernerdschaefer  @peterbourgon  @jmyounker