Updates README for labs/img section

Refactor some stuff and add an URL for Windows users to download the
distro ISOs. It is difficult to copy the URL from the Windows command
prompt.

Change-Id: I12cc40ed733fd36feac4f4d6ae31a9b85999fff9

labs/img/README.rst

@@ -1,3 +1,26 @@
+OsBash
+------
+
+About
+-----
+
 By default, osbash will put into this directory its base disk images
 (base-*-<distro>.vdi), the VM export images (oslabs-<distro>.ova),
 and all installation ISO images it may download.
+
+    - 'img' folder stores all the base disk and ISO images.
+    - To find individual virtualbox disk images, please look into the
+      virtualbox default machine folder.
+      - For Linux: "~/VirtualBox/oslabs/"
+      - In case your default folder is at another location (manually set)
+        please get the location by opening the VirtualBox GUI at this location
+        "File>Preferences>General>Default Machine Folder"
+
+Windows
+-----
+
+For people using windows, you might have to download the iso image for the
+required distro and version manually.
+
+- Ubuntu 14.04 ISO
+  - http://releases.ubuntu.com/14.04/ubuntu-14.04.2-server-amd64.iso