Create index_de.html

German translation of the ODD website
Update index_pl.html

Added link to German translation
Update index_pt.html

Added link to German translation
Update index_de.html

Added link to German translation
Update index_fr.html

Added link to German translation
Update index_it.html

Added link to German translation
Update index.html

Added link to German translation
Merge pull request #14 from ddie/gh-pages

German translation added