Keep info about carbons inside session table

Accordingly, Mnesia/SQL/Riak table 'carboncopy' is not used anymore
and can be safely removed.

As a consequence, the commit deprecates the following options of
mod_carboncopy:
- ram_db_type
- use_cache
- cache_size
- cache_missed
- cache_life_time

Fixes #2663

include/mod_carboncopy.hrl

@@ -1,27 +0,0 @@
-%%%----------------------------------------------------------------------
-%%%
-%%% ejabberd, Copyright (C) 2002-2018   ProcessOne
-%%%
-%%% This program is free software; you can redistribute it and/or
-%%% modify it under the terms of the GNU General Public License as
-%%% published by the Free Software Foundation; either version 2 of the
-%%% License, or (at your option) any later version.
-%%%
-%%% This program is distributed in the hope that it will be useful,
-%%% but WITHOUT ANY WARRANTY; without even the implied warranty of
-%%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-%%% General Public License for more details.
-%%%
-%%% You should have received a copy of the GNU General Public License along
-%%% with this program; if not, write to the Free Software Foundation, Inc.,
-%%% 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
-%%%
-%%%----------------------------------------------------------------------
-
--type matchspec_atom() :: '_' | '$1' | '$2' | '$3' | '$4'.
--record(carboncopy, {us       :: {binary(), binary()} | matchspec_atom(), 
-		     resource :: binary() | matchspec_atom(),
-		     version  :: binary() | matchspec_atom(),
-		     node = node() :: node() | matchspec_atom()}).
-
--define(CARBONCOPY_CACHE, carboncopy_cache).