Add docker run example with environment settings

Example: increase memory allocation for extractor run time

Readme.md

@@ -48,6 +48,9 @@ Models and resources are embedded by default in the docker image.
 + Start default image `docker run -p 8080:8080 -t limsi-source-extractor`
 + Start named default image `docker run --name limsi-extractor -p 8080:8080 -t limsi-source-extractor`
 
+Note: Memory usage can be setup with JAVA_OPTS in the docker command line:
+ `docker run --name limsi-extractor -p 8080:8080 -e JAVA_OPTS='-Xmx3g' -d limsi-source-extractor`
+ 
 ####Custom resources/lib
 Build image can be used with new training set. In this case it is possible to overwrite default model configuration.
 
@@ -71,6 +74,7 @@ In the docker image volumes have been setup to mount new resources.
 + Remove image `docker rmi <image_name>`
 + Load image from file `docker load < image_file.tar`
 + Export image `docker export > image_file.tar`
++ Set environment variables  `docker run -e JAVA_OPTS=`
 
 
 ## Test