Sam Saffron 4c6a0313f2 FEATURE: improve stats provided by rake db:stats
New stats include index size and sort by index + table size

Eg:

```
table_name                  | row_estimate | table_size | index_size | total_size
--------------------------------------------------------------------------
topic_views                 | 18260776     | 796 MB     | 2015 MB    | 2811 MB
post_timings                | 15813837     | 668 MB     | 1153 MB    | 1821 MB
posts                       | 386890       | 1532 MB    | 215 MB     | 1747 MB
post_search_data            | 317575       | 580 MB     | 162 MB     | 742 MB
incoming_emails             | 34412        | 734 MB     | 7160 kB    | 741 MB
incoming_links              | 5169302      | 306 MB     | 377 MB     | 683 MB
email_logs                  | 5            | 32 kB      | 418 MB     | 418 MB
topic_users                 | 2410166      | 217 MB     | 155 MB     | 372 MB
user_actions                | 1361253      | 101 MB     | 266 MB     | 366 MB
...

```
2019-08-02 17:25:42 +10:00
..
2019-05-13 09:55:44 +08:00
2019-05-28 16:57:55 +08:00
2019-08-01 09:12:05 +01:00