droplet.ForceHypervisor for binding it there

Signed-off-by: Jeff Carr <jcarr@wit.com>

droplet.proto

@@ -32,6 +32,7 @@ message Droplet {
         int64   starts          = 17;           // how many times a start has been attempted
         string  current_hypervisor = 18;        // the current hypervisor the droplet is running on
         google.protobuf.Timestamp last_poll = 19;  // the last time we heard anything from this droplet
+	string	force_hypervisor = 20;          // use this hypervisor and this hypervisor only
 }
 
 enum DropletState {

helpers.go

@@ -124,3 +124,7 @@ func (c *Cluster) BlankFields() {
 		d.CurrentState = 0
 	}
 }
+
+func (c *Cluster) AppendEvent(e *Event) {
+	c.Events = append(c.Events, e)
+}