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.

Note: diff best viewed/understood while ignoring whitespace via https://github.com/ManageIQ/manageiq/pull/202/files?w=1

File.read makes this simpler... `File.read(path)`