Make ResourceVersion a string internally instead of uint64

Allows us to define different watch versioning regimes in the future
as well as to encode information with the resource version.

This changes /watch/resources?resourceVersion=3 to start the watch at
4 instead of 3, which means clients can read a resource version and
then send it back to the server. Clients should no longer do math on
resource versions.

pkg/api/ref_test.go

@@ -37,7 +37,7 @@ func TestGetReference(t *testing.T) {
 			obj: &Pod{
 				TypeMeta: TypeMeta{
 					ID:              "foo",
-					ResourceVersion: 42,
+					ResourceVersion: "42",
 					SelfLink:        "/api/v1beta1/pods/foo",
 				},
 			},
@@ -46,14 +46,14 @@ func TestGetReference(t *testing.T) {
 				APIVersion:      "v1beta1",
 				Name:            "foo",
 				UID:             "foo",
-				ResourceVersion: 42,
+				ResourceVersion: "42",
 			},
 		},
 		"serviceList": {
 			obj: &ServiceList{
 				TypeMeta: TypeMeta{
 					ID:              "foo",
-					ResourceVersion: 42,
+					ResourceVersion: "42",
 					SelfLink:        "/api/v1beta2/services",
 				},
 			},
@@ -62,14 +62,14 @@ func TestGetReference(t *testing.T) {
 				APIVersion:      "v1beta2",
 				Name:            "foo",
 				UID:             "foo",
-				ResourceVersion: 42,
+				ResourceVersion: "42",
 			},
 		},
 		"badSelfLink": {
 			obj: &ServiceList{
 				TypeMeta: TypeMeta{
 					ID:              "foo",
-					ResourceVersion: 42,
+					ResourceVersion: "42",
 					SelfLink:        "v1beta2/services",
 				},
 			},