Improve doc about installing and booting Fuel

user-guide
- initialize-fuel/0400-pxe-config -- added note that changing IP here changes CIDR
- initialize-fuel/0500-boot-fuel -- made this a top-level header
  - Added instructions for using a second NIC to access Fuel UI
- initialize-fuel/0600-boot-nodes -- made this a top-level header
  - Modified the instructions to log into the Fuel console to "if you have not already"

- 2000-deploy-environment
  - created an "Install Fuel" subsection and pulled together the pieces
    that were scattered through the next couple of sections.  A couple
    of the subsections were superfluous so I deleted those headers.
  - Added instructions to set the boot order with the hard drive
  - Added instructions to remove the installation media after installation completes
  - Moved the include line for 0400-pxe-config to the end of "Install"
  - Deleted "Initialize Fuel" and the table of steps --it just added an
    unnecessary level of complexity
  - Modified the instructions at the beginning of "Create Environment"
    to reflect that they should have already logged in

Change-Id: I99b01611bf6b6efef457469e442b49ef5bcfbef0
Improve links and graphics for networking docs

ref-arch
- neutron-intro/0260-neutron-config -- added link to "Logical networks"
- nova-intro/0680-nova-vlan-plan -- added tag, link to "Logical networks"
- deleted table with embedded network drawings; the build tools are having
  fits with this and it just duplicates information in the next two sections.

terminology
- networking -- added xref to "Changing PXE Network Parameters During Installation"
- nova-network -- fixed xref to ref-arch section, added xref to network planning
- VLAN -- added xrefs to ref-arch and user-guide

Change-Id: I67c494ec359f3304ed70eb03b78f4ba070bcafdf
Enhancements to the vCenter docs

Pre-install/7000-vcenter-plan -- add link to vCenter installation docs and
summarize the requisite steps, with screen shots.

Ref-arch/logical-setup/7000-vcenter -- corrected info about vCenter driver
for OpenStack. Added reference architecture and network topology diagrams

User-guide/vcenter.rst -- Added complete descriptions with screen shots

General: left-justified all screen shots to match the rest of the guide
and to avoid a tools bug that is sometimes doing odd things with graphics
for which :align" is specified.

relnotes/050-known-issues -- added LP to vCenter HA limitation

Closes-Bug: 1325690

Change-Id: I1ff4369a8ab03ff91f3e3c9cdebfde8a60d56808