Change minion to node

Contination of #1111

I tried to keep this PR down to just a simple search-n-replace to keep
things simple.  I may have gone too far in some spots but its easy to
roll those back if needed.

I avoided renaming `contrib/mesos/pkg/minion` because there's already
a `contrib/mesos/pkg/node` dir and fixing that will require a bit of work
due to a circular import chain that pops up. So I'm saving that for a
follow-on PR.

I rolled back some of this from a previous commit because it just got
to big/messy. Will follow up with additional PRs

Signed-off-by: Doug Davis <dug@us.ibm.com>

pkg/api/serialization_test.go

@@ -331,7 +331,7 @@ func TestBadJSONRejection(t *testing.T) {
 		t.Errorf("Did not reject despite use of unknown type: %s", badJSONUnknownType)
 	}
 	/*badJSONKindMismatch := []byte(`{"kind": "Pod"}`)
-	if err2 := DecodeInto(badJSONKindMismatch, &Minion{}); err2 == nil {
+	if err2 := DecodeInto(badJSONKindMismatch, &Node{}); err2 == nil {
 		t.Errorf("Kind is set but doesn't match the object type: %s", badJSONKindMismatch)
 	}*/
 }