Add script for docker events/metrics and support running TA outside of Splunk

* Add docker.sh and docker_metric.sh for collecting docker events/metrics
* Add helper script to extra/ to run the TA commands on systems without
  a Splunk forwarder. The commands can be sent to a syslog server.
  This script is useful for systems with small or read-only filesystems that
  cannot support a Universal Forwarder.
* Add syslog_inputs_nix_ta app to extra/ for ingesting the data from syslog

default/props.conf

@@ -91,6 +91,15 @@ FIELDALIAS-dest_nt_host = dest_host as dest_nt_host
 ## Scripted Metric Inputs
 #########################
 
+[docker_metric]
+SHOULD_LINEMERGE=false
+LINE_BREAKER = ([\r\n]+)
+KV_MODE = json
+NO_BINARY_CHECK = true
+TRUNCATE=1000000
+TRANSFORMS-docker-metric-dimensions=eval_dimensions
+METRIC-SCHEMA-TRANSFORMS=metric-schema:extract_metrics_docker
+
 [vmstat_metric]
 SHOULD_LINEMERGE=false
 LINE_BREAKER=(^$|[\r\n]+[\r\n]+)
@@ -506,6 +515,14 @@ TRUNCATE=1000000
 DATETIME_CONFIG = CURRENT
 KV_MODE=multi
 
+[docker]
+SHOULD_LINEMERGE=false
+LINE_BREAKER=(^$|[\r\n]+[\r\n]+)
+TRUNCATE=1000000
+KV_MODE = json
+FIELDALIAS-dest_for_docker = host as dest
+FIELDALIAS-src_for_docker = host as src
+
 [vmstat]
 LINE_BREAKER=(^$|[\r\n]+[\r\n]+)
 TRUNCATE=1000000