Ribbon should allow discovery across all namespaces

[piomin]

Is your feature request related to a problem? Please describe.
Ribbon should allow discovery across all namespaces. Currently it search for serivces only in the current namespace.

Describe the solution you'd like
Ribbon auto-configuration needs to be changed. and property allNamespaces should be add with default value false

Describe alternatives you've considered
We could also base on existing property spring.cloud.kubernetes.discovery.all-namespaces

[piomin]

I decided to add new property for enabling it: spring.cloud.kubernetes.ribbon.allNamespaces - following current approach in Spring Cloud Kubernetes module.
Because Kubernetes allows the same app name in different namespaces I'm checking if there more than one serviceId returned by KubernetesClient in the list endpoints from all namespaces.