Replace old Web Registration/Email Registration with modern equiv.

A question on IRC asked how to enable non-registered users to send
email to a tracker and have it accepted.

Found that the admin doc had the old (pre 0.6.0) settings listed for
web and email access.  Updated to the pair of settings that are
currently used.

Author: rouilj

doc/admin_guide.txt

@@ -474,10 +474,10 @@ In both cases, Roundup's behaviour when dealing with unknown users is
 controlled by Permissions defined in the "SECURITY SETTINGS" section of the
 tracker's ``schema.py`` module:
 
-Web Registration
+Web Access and Register
   If granted to the Anonymous Role, then anonymous users will be able to
   register through the web.
-Email Registration
+Email Access and Register
   If granted to the Anonymous Role, then email messages from unknown users
   will result in those users being registered with the tracker.