Enhancement to Show External Authentication Configuration

- Added new entry in the appliance console summary screen
to show a new "External Auth:" entry indiciating either
"not configured" or the IPA Server hostname.
- Also showing current external authentication configuration
before giving the option to unconfigure.
Simplify OpsController::Diagnostics#log_depot_build_edit_screen

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Fix typo

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Remove unnecessary verify and validate methods for log_depot_settings

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Remove credential validation from creation

FileDepotNfs.create!(:uri => "nfs://test") fails because of missing credentials
https://bugzilla.redhat.com/show_bug.cgi?id=965889
Add #verify_credentials methods to appropriate FileDepot subclasses

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Change FileDepot ::SUPPORTED_DEPOTS to #supported_depots

Build a hash of subclass => display_name for all descendants
https://bugzilla.redhat.com/show_bug.cgi?id=965889
Update drop-down to to get the correct uri_prefix based on the model

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Add support_case and depot_name to the edit screen where appropriate

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Add reverse relationship for MiqServer#log_file_depot

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Create log_file_depot using relationships

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Simplify all the things

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Ensure that all FileDepots are subclassed

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Simply state that we are checking whether credentials are required

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Fix validations for MiqSchedule backup depots

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Preload subclasses of FileDepot so that they appear in supported_depots

Rename FileDepotFtpAnonymous to follow our standard subclass naming
https://bugzilla.redhat.com/show_bug.cgi?id=965889
Leverage the dictionary to provide display names for the FileDepots

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Remove Red Hat references

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Set default_value_for PxeServer#customization_directory

https://bugzilla.redhat.com/show_bug.cgi?id=1081006
Migrate any PXE server #customization_directory that is nil to ""

https://bugzilla.redhat.com/show_bug.cgi?id=1081006