Major enhancements to ODT export

This implements most parts of what I requested in https://sourceforge.net/apps/phpbb/freeplane/viewtopic.php?f=1&t=531 and https://sourceforge.net/apps/phpbb/freeplane/viewtopic.php?f=1&t=531.

ODT export now honors

* Automatic layout mode (both all-nodes an non-leaf-node-mode)

  As in the map, styles are applied to nodes up to level 4. Automatic
  layout mode overrules nodes styles, as it does in the map.

* Freeplane pre-defined styles (default styles)

  Style-names are not yet localized and not yet capitalized.

* Custom styles

  Style names are takes as given by the user, some properties (font-size, color, background-color)will be transferred.

* Numbering of nodes with node-numbering set

* Folded nodes will become bullet-lists, but "always unfold" is still honored.

For details please refer to the documentation in freeplane/external-resources/xslt/mm2oowriter.xsl

Todo
* Capitalize pre-defined style-names.