UEC installer and autoregistration improvements

Discussion notes:

=== 10.04 features retrospective ===
 * Node type publication (all node types)
 * Topology detection (start of installer)
 * Key distribution (end of installer)
 * Network setup (end of installer)
 * Autoregistration system (at start time)

=== 10.10 plans ===
 * Refactor installer/package postinst for better package-based install
  * finish-install tasks, for reference:
   * Install parent SSH key
   * Install self SSH key
   * Generate preseed for children (bug 494634)
   * eucalyptus.conf settings (VNET_*INTERFACE)
    * perhaps just allow a blob to append to eucalyptus.local.conf?
      * difficult, as it's hard to add multi-line values to a preseed file
    * requires replacing netcfg-specific handling with something that (perhaps?) looks at `/etc/network/interfaces`
   * Setup bridge device on NC
  * eucalyptus-udeb.postinst asks a bunch of questions used by finish-install; it is necessary to analyse these to determine which would need to be asked in the event of a package-based installation
 * Autoregistration fixes
  * NC publication job should support specific IP (bug 549022)
  * ability to completely disable auto-registration at install time and while running (ie no avahi broadcast) -- eucalyptus/autoregistration ?
    * preseed eucalyptus/nobroadcast ??
    * Stop publication when the thing is registered
      * NC: yes
      * CLC/Walrus/CC/SC: would prevent discovery for future installs, maybe be optional

=== Idea brainstorm zone ===
 * Allow all-in-one (with NC) install?
  * perhaps useful for a single, massive machine (ie, 16 cpus, or something)
  * BAD IDEA
 * CLC Avahi publication does not advertise "cloud name", so if you install multiple clouds on a single network then it can be confusing. There is no "cloud name" in Eucalyptus. The assumption is one cloud per network.