Add a Mindmaps representing the current menu structures.

The mindmap was generated using helper-xslt for building a mind-map
out of ´*menu.xml`, texts have been inserted from
translations/Resources_en.properties (using a script) and styles have
been added.

The result as generated by
  xsltproc freeplane/ant/mm2menu.xsl \
    freeplane/resources/xml/$menu.mm \
    > freeplane/resources/xml/$menu.xml
(with $menu being one of mindmapmodemenu, filemodemenu, stylemodemenu)
has been verified to result in the same file as the current
`$menu.xml`.

Also add a build-rule to not include the mindmaps in the distribution.
Remove the helper-xslt now the conversion is done.
Add ant-tasks to build `preferences.xml` and `*menu.xml` from Mindmap.
Plugins: Generate `preferences.xml` from a mind-maps.

Includes ant-tasks for building and cleaning.
Add .gitignore for the `preferences.xml` files which are now built.
Add a Mindmap representing the current `appletMenu` structures.

Includes an ant-task for building.
Fix: xml-files generated from mind-maps are not cleaned.
Add xml-files generated from mind-maps to .gitignore.
Add some descriptions to the menu mind-maps and enhance styles.

These have not been translated when processing by a script in
2013-06-02T20:33:14Z!h.goebel@crazy-compilers.com.