[doc] /etc/default/<normalizedName> is a shell script (cf #473)

src/sphinx/archetypes/java_server/customize.rst

@@ -34,6 +34,7 @@ Create ``src/templates/etc-default`` with the following template
     # ${{daemon_user}}      daemon user
     # -------------------------------------------------
 
+    # Using $JAVA_OPTS envars
     # Setting -Xmx and -Xms in Megabyte
     # -mem 1024
 
@@ -58,9 +59,16 @@ Create ``src/templates/etc-default`` with the following template
     # using a reserved parameter. See #184
     # -d -- -d
 
+    # Example:
+    # JAVA_OPTS=" -Dpidfile.path=/var/run/${{app_name}}/play.pid $JAVA_OPTS"
+    # JAVA_OPTS=" -mem 1024 -Dkey=val -jvm-debug $JAVA_OPTS"
+
 The file will be installed to ``/etc/default/<normalizedName>`` and read from there
 by the startscript.
 
+*Beware the format changed from java option list only to shell script setting Environment Variables
+Project using previous version would adapt their configuration file.*
+
 Environment variables
 ~~~~~~~~~~~~~~~~~~~~~