Project architecture design document

This is architecture proposal for MVP version of the product. When MVP
is done it'll be revisited to verify whether it (still) works well.

docs/design/architecture.md

+# Architecture 
+Kubernetes Console project consists of two main components. They are called here the
+frontend and the backend.
+
+The frontend is a single page web application that runs in a browser. It fetches all its
+business data from the backend using standard HTTP methods. It does not implement business logic;
+it only presents fetched data and sends requests to the backend for actions.
+
+The backend runs in a Kubernetes cluster as a kubernetes service. Alternatively, it may run anywhere
+outside of the cluster, given that it can connect to the master. The backend is a HTTP server that
+proxies data requests to appropriate remote backends (e.g., k8s apiserver or heapster) or implements
+business logic. The backend implements business logic when remote backends APIs do not provide
+support required use case directly, e.g., “I want to get a list of pods with their CPU usage metric
+timeline”. Figure 1 outlines the architecture of the project.
+
+![Architecture Overview](architecture.png?raw=true "Architecture overview")
+*Figure 1: Project architecture overview*
+
+Rationale for having a backend that implements business logic:
+
+* Clear separation between the presentation layer (frontend) and business logic layer (backend).
+This is because every action goes through API.
+* Transactional actions are easier to implement on the backend than on the frontend. Examples of
+such actions: "Create a replication controller and a service for it" or "Do a rolling update".
+* Possible code reuse from existing tools (e.g., kubectl) and upstream contributions to the tools.
+* Speed: getting composite data from beckends is faster on the backend (if it runs close to the
+data sources). For example, getting a list of pods with their CPU utilization timeline
+requires at least two requests. Doing them on the backend shortens RTT.