use shared classloader so other plugins can contribute functions

fixes #81

pom.xml

@@ -194,9 +194,11 @@
             </resource>
             <resource>
                 <directory>src/main/resources</directory>
-                <excludes>
-                    <exclude>**/*.properties</exclude>
-                </excludes>
+                <includes>
+                    <include>**/version.properties</include>
+                    <include>**/graylog-plugin.properties</include>
+                </includes>
+                <filtering>true</filtering>
             </resource>
         </resources>
         <pluginManagement>

src/main/resources/org.graylog.plugins.graylog-plugin-pipeline-processor/graylog-plugin.properties

@@ -0,0 +1,12 @@
+# The plugin version
+version=${project.version}
+
+# The required Graylog server version
+graylog.version=${graylog.version}
+
+# When set to true (the default) the plugin gets a separate class loader
+# when loading the plugin. When set to false, the plugin shares a class loader
+# with other plugins that have isolated=false.
+#
+# Do not disable this unless this plugin depends on another plugin!
+isolated=false