Support SHOW STATS for specific module

[otoolep]

The reference to host is obsolete. We may add it back in at some point, but it was not currently being used.

Example output:

> SHOW STATS
name: engine
tags: path=/home/philip/.influxdb/data/_internal/monitor/1, version=bz1
blks_write      blks_write_bytes        blks_write_bytes_c      points_write    points_write_dedupe
----------      ----------------        ------------------      ------------    -------------------
70              4917                    4279                    70              70


name: httpd
tags: bind=:8086
query_req       query_resp_bytes        req
---------       ----------------        ---
6               2268                    6

name: shard
tags: engine=bz1, id=1, path=/home/philip/.influxdb/data/_internal/monitor/1
fields_create   series_create   write_points_ok write_req
-------------   -------------   --------------- ---------
0               6               64              11

name: runtime
-------------
Alloc   Frees   HeapAlloc       HeapIdle        HeapInUse       HeapObjects     HeapReleased    HeapSys Lookups Mallocs NumGC   NumGoroutine    PauseTotalNs    Sys             TotalAlloc
3737136 12003   3737136         2932736         4407296         13398           0               7340032 135     25401   2       43              1295888         11737336        11167896

> SHOW STATS FOR 'httpd'
name: httpd
tags: bind=:8086
query_req       query_resp_bytes        req
---------       ----------------        ---
7               3515                    7

> SHOW STATS FOR 'cluster'
> 

[otoolep]

@dgnorton @corylanou

[corylanou]

+1