Plugin assembly: Allow .html, .xml and .properties files to be filtered by Maven

Motivation:
Give third-party developers more flexibility to build their plugins. Currently it's not possible to filter anything besides the plugin.xml.

Further improvements:
- Include lib folder in the assembly (for non-Maven artifacts)
- Update namespace "http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2" -> "http://maven.apache.org/ASSEMBLY/2.0.0"

src/plugins/openfire-plugin-assembly-descriptor/src/main/resources/assemblies/openfire-plugin-assembly.xml

-<assembly
-        xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2"
-        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-        xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2 http://maven.apache.org/xsd/assembly-1.1.2.xsd">
+<assembly xmlns="http://maven.apache.org/ASSEMBLY/2.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+          xsi:schemaLocation="http://maven.apache.org/ASSEMBLY/2.0.0 http://maven.apache.org/xsd/assembly-2.0.0.xsd">
     <id>openfire-plugin-assembly</id>
     <formats>
         <format>jar</format>
@@ -14,10 +12,20 @@
             <outputDirectory/>
             <directory>${project.build.sourceDirectory}/../..</directory>
             <includes>
-                <include>*.html</include>
                 <include>*.gif</include>
                 <include>*.png</include>
-                <include>classes/**</include>
+                <include>lib/**</include>
+            </includes>
+        </fileSet>
+
+        <!-- filtered metadata files (html, plugin.xml) -->
+        <fileSet>
+            <outputDirectory/>
+            <directory>${project.build.sourceDirectory}/../..</directory>
+            <filtered>true</filtered>
+            <includes>
+                <include>*.html</include>
+                <include>plugin.xml</include>
             </includes>
         </fileSet>
 
@@ -30,14 +38,34 @@
                 <include>i18n/**</include>
                 <include>web/**</include>
             </includes>
-            <!-- Don't include jsp pages, they will be compiled -->
+            <!-- Exclude jsp pages (they will be compiled) and filterable resources -->
             <excludes>
                 <exclude>**/*.jsp</exclude>
+                <exclude>i18n/**/*.properties</exclude>
+                <exclude>web/**/*.xml</exclude>
+                <exclude>web/**/*.html</exclude>
+                <exclude>web/**/*.properties</exclude>
+            </excludes>
+        </fileSet>
+
+        <!-- database, i18n and web directory (filtered) -->
+        <fileSet>
+            <outputDirectory/>
+            <directory>${project.build.sourceDirectory}/..</directory>
+            <filtered>true</filtered>
+            <includes>
+                <include>i18n/**/*.properties</include>
+                <include>web/**/*.xml</include>
+                <include>web/**/*.html</include>
+                <include>web/**/*.properties</include>
+            </includes>
+            <excludes>
+                <!-- Exclude the web.xml, it will be generated by JspC -->
                 <exclude>web/WEB-INF/web.xml</exclude>
             </excludes>
         </fileSet>
 
-        <!-- web.xml (it will be modified by JspC -->
+        <!-- web.xml (it will be modified by JspC) -->
         <fileSet>
             <outputDirectory>web/WEB-INF</outputDirectory>
             <directory>${project.build.directory}</directory>
@@ -46,16 +74,28 @@
             </includes>
         </fileSet>
 
-    </fileSets>
-
-    <!-- metadata files that need to have content replaced by Maven metadata -->
-    <files>
-        <file>
-            <source>plugin.xml</source>
-            <outputDirectory>/</outputDirectory>
+        <!-- Include the classes folder (filtered) -->
+        <fileSet>
+            <outputDirectory>classes</outputDirectory>
+            <directory>classes</directory>
             <filtered>true</filtered>
-        </file>
-    </files>
+            <includes>
+                <include>**/*.xml</include>
+                <include>**/*.properties</include>
+            </includes>
+        </fileSet>
+
+        <!-- Include the classes folder -->
+        <fileSet>
+            <outputDirectory>classes</outputDirectory>
+            <directory>classes</directory>
+            <filtered>false</filtered>
+            <excludes>
+                <exclude>**/*.xml</exclude>
+                <exclude>**/*.properties</exclude>
+            </excludes>
+        </fileSet>
+    </fileSets>
 
     <!-- Bundle the dependencies of this plugin -->
     <dependencySets>