Settings: External automatic rule settings.

 - Add external automatic rule settings page with the common
   settings for all rules (enabled, name, zen mode).
 - Pull common rule-instance settings into settings base class, share
   with existing schedule rule settings.
 - New page not searchable since it is at the rule-instance level.
 - Obtain external rule information from existing conditions provider
   metadata.  Includes rule type caption, sub-configuration activity,
   and default condition id.
 - If external condition providers exist with the appropriate metadata,
   display the external rule types as options in the new rule dialog.
   (max of 3 external types)
 - Pull common managed service listing code out of common settings base
   class and into a more reusable helper class.

Bug: 20064962
Change-Id: Ibc13607490b7312a7d9f7f3bd61c3cfcf71a2794