Disable DocxFormatter for 'pptx' and 'xlsx' files

Formatting such files fails with some ClassCastException somewhere in
the docx libraries.

Change-Id: I20f525af370af56c10a67b3e05f2a627bbab1551
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

src/main/java/com/googlesource/gerrit/plugins/xdocs/XDocGlobalConfig.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/xdocs/XDocGlobalConfig.java b/src/main/java/com/googlesource/gerrit/plugins/xdocs/XDocGlobalConfig.java
index 05f0f9b..28bfd2c 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/xdocs/XDocGlobalConfig.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/xdocs/XDocGlobalConfig.java
@@ -51,7 +51,7 @@
   static void initialize(Config cfg) {
     cfg.setString(SECTION_FORMATTER, AsciidoctorFormatter.NAME, KEY_EXT, "adoc");
     cfg.setStringList(SECTION_FORMATTER, DocxFormatter.NAME, KEY_EXT,
-        Arrays.asList("docx", "pptx", "xlsx"));
+        Arrays.asList("docx"));
     cfg.setString(SECTION_FORMATTER, ImageFormatter.NAME, KEY_MIME_TYPE,
         "image/*");
     cfg.setString(SECTION_FORMATTER, MarkdownFormatter.NAME, KEY_MIME_TYPE,

src/main/resources/Documentation/about.md

diff --git a/src/main/resources/Documentation/about.md b/src/main/resources/Documentation/about.md
index a15e124..8e4d020 100644
--- a/src/main/resources/Documentation/about.md
+++ b/src/main/resources/Documentation/about.md
@@ -69,7 +69,7 @@
   <tr>
     <td><tt>DocxFormatter</tt></td>
     <td><tt>DOCX</tt></td>
-    <td>Formatter for <tt>.docx</tt>, <tt>.pptx</tt> and <tt>.xlsx</tt> files.</td>
+    <td>Formatter for <tt>.docx</tt> files.</td>
     <td><a href="../../../Documentation/licenses.html#Apache2_0">Apache2.0</a><br/></td>
     <td>
       <a href="http://www.docx4java.org/trac/docx4j">http://www.docx4java.org/trac/docx4j</a></br>