Add comment about time units used in environment variables

Author: wheleph

Hub/Dockerfile.txt

@@ -7,13 +7,19 @@ MAINTAINER Selenium <[email protected]>
 EXPOSE 4444
 
 ENV GRID_THROW_ON_CAPABILITY_NOT_PRESENT true
+# In milliseconds
 ENV GRID_NEW_SESSION_WAIT_TIMEOUT -1
 ENV GRID_JETTY_MAX_THREADS -1
+# In milliseconds
 ENV GRID_NODE_POLLING  5000
+# In milliseconds
 ENV GRID_CLEAN_UP_CYCLE 5000
+# In seconds
 ENV GRID_TIMEOUT 30
+# In seconds
 ENV GRID_BROWSER_TIMEOUT 0
 ENV GRID_MAX_SESSION 5
+# In milliseconds
 ENV GRID_UNREGISTER_IF_STILL_DOWN_AFTER 30000
 
 COPY generate_config /opt/selenium/generate_config