Moved system package inputs out to top level (#4406)

plugins/inputs/system/README.md

@@ -0,0 +1,36 @@
+# System Input Plugin
+
+The system plugin gathers general stats on system load, uptime,
+and number of users logged in. It is similar to the unix `uptime` command.
+
+### Configuration:
+
+```toml
+# Read metrics about system load & uptime
+[[inputs.system]]
+  # no configuration
+```
+#### Permissions:
+
+The `n_users` field requires read access to `/var/run/utmp`, and may require
+the `telegraf` user to be added to the `utmp` group on some systems.
+
+### Metrics:
+
+- system
+  - fields:
+	- load1 (float)
+	- load15 (float)
+	- load5 (float)
+	- n_users (integer)
+	- n_cpus (integer)
+	- uptime (integer, seconds)
+	- uptime_format (string)
+
+### Example Output:
+
+```
+system,host=tyrion load1=3.72,load5=2.4,load15=2.1,n_users=3i,n_cpus=4i 1483964144000000000
+system,host=tyrion uptime=1249632i 1483964144000000000
+system,host=tyrion uptime_format="14 days, 11:07" 1483964144000000000
+```