Add initial thanos support to kube-prometheus

This is distributed as a library that the user is meant to import.
example:

```
kp =  (import 'kube-prometheus/kube-prometheus.libsonnet') +
      (import 'kube-prometheus/kube-prometheus-thanos.libsonnet') +
      {
        _config+:: {...}
      };
```

jsonnet/kube-prometheus/kube-prometheus-thanos.libsonnet

@@ -0,0 +1,64 @@
+local k = import 'ksonnet/ksonnet.beta.3/k.libsonnet';
+local service = k.core.v1.service;
+local servicePort = k.core.v1.service.mixin.spec.portsType;
+
+
+{
+  _config+:: {
+    versions+:: {
+      thanos: 'v0.1.0',
+    },
+    imageRepos+:: {
+      thanos: 'improbable/thanos',
+    },
+  },
+  prometheus+:: {
+    prometheus+: {
+      spec+: {
+        podMetadata+: {
+          labels+: { 'thanos-peer': 'true' },
+        },
+        thanos+: {
+          peers: 'thanos-peers.' + $._config.namespace + '.svc:10900',
+          version: $._config.versions.thanos,
+          baseImage: $._config.imageRepos.thanos,
+        },
+      },
+    },
+    thanosQueryDeployment:
+      local deployment = k.apps.v1beta2.deployment;
+      local container = k.apps.v1beta2.deployment.mixin.spec.template.spec.containersType;
+      local containerPort = container.portsType;
+
+      local thanosQueryContainer =
+        container.new('thanos-query', $._config.imageRepos.thanos + ':' + $._config.versions.thanos) +
+        container.withPorts([
+          containerPort.newNamed('http', 10902),
+          containerPort.newNamed('grpc', 10901),
+          containerPort.newNamed('cluster', 10900),
+        ]) +
+        container.withArgs([
+          'query',
+          '--log.level=debug',
+          '--query.replica-label=prometheus_replica',
+          '--cluster.peers=thanos-peers.' + $._config.namespace + '.svc:10900',
+        ]);
+      local podLabels = { app: 'thanos-query', 'thanos-peer': 'true' };
+      deployment.new('thanos-query', 1, thanosQueryContainer, podLabels) +
+      deployment.mixin.metadata.withNamespace($._config.namespace) +
+      deployment.mixin.metadata.withLabels(podLabels) +
+      deployment.mixin.spec.selector.withMatchLabels(podLabels) +
+      deployment.mixin.spec.template.spec.withServiceAccountName('prometheus-' + $._config.prometheus.name),
+    thanosQueryService:
+      local thanosQueryPort = servicePort.newNamed('http-query', 9090, 'http');
+      service.new('thanos-query', { app: 'thanos-query' }, thanosQueryPort) +
+      service.mixin.metadata.withNamespace($._config.namespace) +
+      service.mixin.metadata.withLabels({ app: 'thanos-query' }),
+    thanosPeerService:
+      local thanosPeerPort = servicePort.newNamed('cluster', 10900, 'cluster');
+      service.new('thanos-peers', { 'thanos-peer': 'true' }, thanosPeerPort) +
+      service.mixin.spec.withType('ClusterIP') +
+      service.mixin.spec.withClusterIp('None'),
+
+  },
+}