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
[email protected]

Review-Url: https://codereview.chromium.org/2164753004
Cr-Commit-Position: refs/heads/master@{#406718}
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index d90eeda..2fad49d 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -186,7 +186,7 @@
         r"^net[\\\/]disk_cache[\\\/]cache_util\.cc$",
         r"^net[\\\/]url_request[\\\/]test_url_fetcher_factory\.cc$",
         r"^remoting[\\\/]host[\\\/]security_key[\\\/]"
-            "gnubby_auth_handler_linux\.cc$",
+            "security_key_auth_handler_linux\.cc$",
         r"^ui[\\\/]base[\\\/]material_design[\\\/]"
             "material_design_controller\.cc$",
         r"^ui[\\\/]gl[\\\/]init[\\\/]gl_initializer_mac\.cc$",