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/service/endpoints_controller.go

@@ -90,7 +90,7 @@ func (e *EndpointController) SyncServiceEndpoints() error {
 		*newEndpoints = *currentEndpoints
 		newEndpoints.Endpoints = endpoints
 
-		if currentEndpoints.ResourceVersion == 0 {
+		if len(currentEndpoints.ResourceVersion) == 0 {
 			// No previous endpoints, create them
 			_, err = e.client.CreateEndpoints(nsCtx, newEndpoints)
 		} else {