Revert of Renaming Gnubby and RemoteSecurityKey files/classes/members

Revert of Renaming Gnubby and RemoteSecurityKey files/classes/members (patchset #4 id:60001 of https://codereview.chromium.org/2162083003/ )

Reason for revert:
Broke GYP build bots.

Original issue's description:
> Renaming Gnubby and RemoteSecurityKey files/classes/members
> 
> This change is a simple refactoring to rename the 'Gnubby' and
> 'RemoteSecurityKey' file/class names/comments/etc to be consistent.
> I've chosen to use 'SecurityKey' as it is shorter that RemoteSecurityKey
> (which was causing too many 80 char limit issues).  No functional
> changes are expected as a result of this change.
> 
> Note: Not every instance of Gnubby or RemoteSecurityKey has been
> changed.  The registry key used for toggling this functionality still
> uses 'gnubby'.  I don't want to change that here.  Also, the process
> used on the host machine is still called remote_security_key so classes
> associated with that process were not renamed (neither were the IPC
> messages used by it).
> 
> BUG=593736
> TBR=jochen@chromium.org
> 
> Committed: https://crrev.com/281516541a3aa129b5a23c29cdfb926c99f3d516
> Cr-Commit-Position: refs/heads/master@{#406435}

TBR=sergeyu@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=593736

[joedow, 2016-07-20 20:31:55]

Created Revert of Renaming Gnubby and RemoteSecurityKey files/classes/members