Documents what debconf does

After discussing the topic on the doc list, it appears that it
would be nice to document what the debconf screens are configuring.
This patch adds the information, so that it makes it more explicit
to our users what Debian does for them.

This patch only addresses the debconf chapter. There will be other
patches for specific services later on, once this patch is merged.

Change-Id: I60c7ba818e36056ed913582e66bf24c41b2c6807
Admin user guide edits

Edits to the Dashboard: Manage Users and Projects section
Edits to the Manage Project Security section
All of this hopefully brings these docs in line w/ the Icehouse GUI
Closes-bug: 1194229

Reviewer comments added and niceness fixes as well.

Change-Id: Ib7ffa484eb817dbda0c046931aedea24e14404cc
Documents vCenter service account requirements

Adds details of required vCenter privileges, and how to allocate
them appropriately.
Made some additional edits - diane fleming

Change-Id: Icc7bdb6bde4844d3c65af10dca711dc38c8a13e6
Closes-Bug: 1272450
Merge "Documents what debconf does"
Merge "Documents vCenter service account requirements"
Merge "Admin user guide edits"