Improvement for #5 and #12

[wangchen615]

To solve and close issue #5, we did the following.

1. Change the Dockerfile to build the binaries so the building process is independent of the machine.
2. Add Makefile for the new Dockerfile.
3. Add manifests/load-watcher-deployment.yaml to allow users to deploy load-watcher as a service in a Kubernetes cluster directly. Please advise if the official docker account needs to be updated.

To solve and close issue #12, we added the following.

1. Add pkg/metricsprovider/loadwatcher.go to allow users use load-watcher libraries in client mode.
2. Add load-watcher-client.go to give an example of using load-watcher libraries in client mode.
3. Change all clients' FetchAllHostsMetrics method's return metrics from map[string][]watcher.Metric to watcher.NodeMetricsMap, so all clients' have the same interface as load-watcher client.
4. Change all clients' FetchAllHostsMetrics method's return metrics from map[string][]watcher.Metric to watcher.WatcherMetrics, so all clients' have the same interface as load-watcher client.
5. Change all clients' FetchHostMetrics method's return metrics from []watcher.Metric to watcher.WatcherMetrics, so all clients' have the same interface as load-watcher client.
6. Add pkg/utils/utils.go to initiate all environment variables and have a unified method to create client according to env setup.
7. Export all client names to be used by pkg/utils/utils.go.

[zorro786]

Left some comments on design

[ridv]

In the interest of not losing comments and change history, I suggest we try to avoid force pushes 😄 Hard to keep track of what was talked about in the past otherwise

[wangchen615]

In the interest of not losing comments and change history, I suggest we try to avoid for

Ok, Will just squash when merge.

[zorro786]

LGTM