Added missing docs.

docs/source/config/inputs/docker_log.rst

@@ -54,6 +54,9 @@ Config:
 
 .. versionadded:: 0.11
 
+- fields_from_labels (array[string], optional):
+    A list of labels to pull is as fields. These are pulled in last and will
+	override any fields added from fields_from_env.
 - since_path (string, optional):
     Path to file where input will write a record of the "since" time for each
     container to be able to not miss log records while Heka is down (see
@@ -69,6 +72,18 @@ Config:
     to zero (e.g. "0s") then the file will only be written out when Heka
     cleanly shuts down, meaning that if Heka crashes all container logs written
     since Heka has started will be re-fetched.
+- container_expiry_days (int, optional):
+    The number of days after which to remove unseen containers from the sinces
+	file. Defaults to 30 days. This prevents containers from building up
+	in the file forever. It has the effect of replaying logs from any container
+	which was not seen for this interval but then re-appears. Containers are
+	tracked by container ID.
+- new_containers_replay_logs (bool, optional):
+    Will newly discovered containers replay all of the logs currently available
+	via the Docker logs endpoint? Defaults to true. If you are upgrading from
+	a previous version of heka, you may want to consider setting this to false
+	when first upgrading to prevent the massive replay of logs from all of
+	your existing containers.
 
 Example: