Working step-by-step CH and CIB instructions

[lukpueh]

This PR provides detailed step-by-step instructions on how to install and deploy clearinghouse and custom installer builder locally, using Virtualenvironments and Apache2 Virtualhosts. The instructions were tested on a Ubuntu 15.10 Desktop Virtualbox.

Most of the instructions are quite similar, i.e. there is potential to DRY them up. Also the instructions to create base installer for the custom installer builder partially repeat what reads in installer-packaging's README.

This is a fix for issue #15.

Please give feedback to whether the instructions are accurate. Also two items should be verified:

• Does CIB instructions need further high-level info?
• Is the software_update_url (http://seattle.cs.washington.edu/couvb/updatesite/0.1/) for softwareupdater.py correct?

[aaaaalbert]

Clarifications:

• There is some higher-level info about the CIB in the infrastructure arch docs, in the installer workflow document (probably most relevant in terms of #15), and also in the overall CIB operating docs.
• The correct softwareupdater URL is http://seattlesoftwareupdater.poly.edu/updatesite/ (as found in the production installer). The current sources get this wrong too, see https://github.com/SeattleTestbed/softwareupdater/blob/master/softwareupdater.py#L62.

[aaaaalbert]

Addendum: The original base installers creation docs.

[aaaaalbert]

Read over the new docs and liked them! I'm merging this to clear the way for future improvements in terms of factoring out duplicate sections etc. Thanks!