[CE-204] Update Cello Docs

This PR adds required documentation to describe
cello-baseimage to cello's-rtd.

Change-Id: Ida7aa0043ae6477a64dcfb8009afd7e48f1c05c9
Signed-off-by: Krishna Harsha Voora <krishvoor@in.ibm.com>

docs/arch.md

@@ -43,4 +43,4 @@ The reasons of choosing it include:
 * Flexible for extending
 * Stable in code
 
-<a rel="license" href="http://creativecommons.org/licenses/by/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/l/by/4.0/88x31.png" /></a><br />This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution 4.0 International License</a>.
+<a rel="license" href="http://creativecommons.org/licenses/by/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/l/by/4.0/88x31.png" /></a><br />This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution 4.0 International License</a>.

docs/setup_master.md

@@ -26,6 +26,7 @@ You may check `git` and `make` are installed to clone the code.
 $ sudo aptitude install git make -y
 $ git clone http://gerrit.hyperledger.org/r/cello && cd cello
 ```
+
 ### Run Setup
 
 For the first time running, please setup the master node with the [setup.sh](https://github.com/hyperledger/cello/blob/master/scripts/master_node/setup.sh).
@@ -85,6 +86,18 @@ In MacOS, Docker cannot mount local path from host by default. Hence for mongo c
 * Make sure the `/opt/cello` path exists locally, and it is writable for the current user account. `make setup-master` should handle this already.
 * Add the path to sharing list in the preference of [Docker for MacOS](https://docs.docker.com/docker-for-mac/install/), to make it mountable by container.
 
+## Cello Baseimage
+![BaseImage](imgs/cello_baseimage.png)
+
+The purpose of this baseimage is to act as a bridge between a raw ubuntu/xenial configuration and the customizations
+required for supporting a Hyperledger Cello environment. The build process is generally expensive so it is fairly
+inefficient to JIT assemble these components on demand. Hence bundled into baseimage and subsequently cached on
+the public repositories, so they can be simply consumed without requiring a local build cycle.
+
+### Usuage
+* "make docker" will build the docker images and commit it to your local environment; e.g. "hyperledger/cello-baseimage".
+The docker image is also tagged with architecture and release details.
+
 ### More Commands using make
 
 To know more what the following make commands does please refer [make_support](./make_support.md) page.