odt2mediawiki.xsl: improve export filter

Replace <text>&#10;</text> with <value-of select="$NL"/>

Image
 + Add the alternative text in a image
 + Add support for image align with wrap='none'

Paragraph
 + Replace <center></center> tags
 + Add support for background-color and font-color

Table:
 * Cell:
   + Use align element
   + Add support for background-color and font-color
   + If all cells have the same style then specify that in the row section

 * Table:
   + Add support for table align and table width

 * Row:
   + Fix new line at the end of the row

 * Header
   + Treat the header like the row

Text:
 + Add support for background-color and font-color

Change-Id: Icd7196006b6d06d6c0c030d967686ed8f8a5e454
Reviewed-on: https://gerrit.libreoffice.org/15391Tested-by: David Tardon <dtardon@redhat.com>
Reviewed-by: David Tardon <dtardon@redhat.com>