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

sql/mysql.new.sql

@@ -403,17 +403,6 @@ CREATE TABLE bosh (
 
 CREATE UNIQUE INDEX i_bosh_sid ON bosh(sid(75));
 
-CREATE TABLE carboncopy (
-    username text NOT NULL,
-    server_host text NOT NULL,
-    resource text NOT NULL,
-    namespace text NOT NULL,
-    node text NOT NULL,
-    PRIMARY KEY (server_host(191), username(191), resource(191))
-) ENGINE=InnoDB CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
-
-CREATE INDEX i_carboncopy_sh_user ON carboncopy (server_host(191), username(75));
-
 CREATE TABLE proxy65 (
     sid text NOT NULL,
     pid_t text NOT NULL,