postgres: get stats tagged by table/index

[clofresh]

Some nice stats broken down by table or index:

=> \d pg_stat_user_indexes 
View "pg_catalog.pg_stat_user_indexes"
    Column     |  Type  | Modifiers 
---------------+--------+-----------
 relid         | oid    | 
 indexrelid    | oid    | 
 schemaname    | name   | 
 relname       | name   | 
 indexrelname  | name   | 
 idx_scan      | bigint | 
 idx_tup_read  | bigint | 
 idx_tup_fetch | bigint | 

=> \d pg_stat_user_tables 
          View "pg_catalog.pg_stat_user_tables"
      Column      |           Type           | Modifiers 
------------------+--------------------------+-----------
 relid            | oid                      | 
 schemaname       | name                     | 
 relname          | name                     | 
 seq_scan         | bigint                   | 
 seq_tup_read     | bigint                   | 
 idx_scan         | bigint                   | 
 idx_tup_fetch    | bigint                   | 
 n_tup_ins        | bigint                   | 
 n_tup_upd        | bigint                   | 
 n_tup_del        | bigint                   | 
 n_tup_hot_upd    | bigint                   | 
 n_live_tup       | bigint                   | 
 n_dead_tup       | bigint                   | 
 last_vacuum      | timestamp with time zone | 
 last_autovacuum  | timestamp with time zone | 
 last_analyze     | timestamp with time zone | 
 last_autoanalyze | timestamp with time zone | 

[alq666]

Implemented in #760