option to override listening port (#604)

in my case, somehow running everything in single deployment pod i got error complaining that 8080 is already taken, and did not found any docs here about ability to change it

README.md

@@ -166,3 +166,4 @@ For example, if you want to use an environment variable to set the `name` parame
 |`KAFKA_CLUSTERS_0_KAFKACONNECT_0_ADDRESS` |Address of the Kafka Connect service endpoint 
 |`LOGGING_LEVEL_ROOT`        	| Setting log level (all, debug, info, warn, error, fatal, off). Default: debug
 |`LOGGING_LEVEL_COM_PROVECTUS`        	|Setting log level (all, debug, info, warn, error, fatal, off). Default: debug
+|`SERVER_PORT` |Port for the embedded server. Default `8080`