Adding the following accross the project:

```bash
/# exit immediately when a command fails
set -e
/# only exit with zero if all commands of the pipeline exit successfully
set -o pipefail
/# error on unset variables
+set -u

```

Previously the script errored out, as ServiceMonitor objects are only
registered once the Prometheus Operator is running.

The current example-app setup in the kube-prometheus project is able to
discover scraping targets in the default namespace. It is not able to
discover the configured Alertmanager in the monitoring namespace.

This patch adds an alertmanager-discovery rbac role, to permit the
above described action. In addition it does the following cleanups:

- Remove kubeconfig configuration in deploy and teardown script. kubectl
chooses .kube/config whenever KUBECONFIG is not set by default

- Remove namespace specification option via NAMESPACE env var. In most
of the manifests the metadata/namespace was hardcoded anyways, in
addition in the promtheus frontend role binding the service account
namespace is hardcoded to default as well.

- Instead of `kubectl {apply,delete}` individual manifests, the deploy
and teardown shell scripts {apply,delete} on the entire folder.

In some cases we have been using `alert-rules` in some cases
`prometheus-rulefiles`. This led to confusion [1]. Instead, unify the
Prometheus rules configmap labels to:

```yaml
labels:
  role: alert-rules
```

[1] https://github.com/coreos/prometheus-operator/issues/1102

added service account, role and role binding for the prometheus frontend
example, also updated prometheus to use the correct service account

fixes #1049

Might as well, right?

Bump prometheus to 2.0.0, prometheus-operator to 0.15.0, alertmanager to 0.12.0 and node-exporter to 0.15.1, grafana to 4.6.3
migrate prometheus alerts to yaml notation

NAMESPACE feature in scripts implies it works. warnning ensures
that users are aware that its use requires further changes.

Alleviates #765

Per issue 593, append .yml to each filename used in the generated configmap. I wasn't able to see alerts in the Prometheus UI until I did this

The merge was missing a new line at the end of the merge, so only
the first datasource was being put into the ConfigMap.

In the generated version of this file at /contrib/kube-prometheus/manifests/grafana/grafana-deployment.yaml the version was bumped to 4.5.2 but seems it was overlooked in this templated version of the file.