fixes #1814 - converts sp_* attributes into a BMC interface class

this patch also includes the following

• added a new interfaces table, and STI objects to represent a NIC, BMC, Managed
  and a bootable interface.
• refactored DHCP/DNS orchestation code, so they can work on the...

refs #1991 - Cache not cleared prevent location / org feature to show up

1. ensures settings cache is removed when app starts
we can't remove all cache, with Rails.cache.clear as that might lead to issues
with people using memcache with multiple foreman instances (e.g. we can clear...

renamed to thread_session.rb

fixes #2061 - test if oVirt API has HTTPS redirect

rest_client will refuse to follow redirects on POST requests, so the URL must
be entered as HTTPS. Don't require HTTPS as dev environments may be HTTP-only.

fixes #2062 - Add max_trends setting

added slash /unattended to other url_for calls

refs #2023 - always write using_storeconfigs default as a boolean

minor cleanups to the proxy resource class refs #2056

fixes # 2056 - add bmc support to the api-proxy class

fixes #2030 - define instance variables during ERB evaluation when not using safemode

Thanks to Paavo Pokkinen <paavo.pokkinen@faarao.fi>