Add support for robots noimageindex and notranslate

Here is a patch adding this functionality. ;)

Damien,

Thank you for committing this patch.

Looks like there was a change in the 'notranslate' tag description from:
'Prevent search engines from offering translation of this page in search results.'
to:
'Prevent search engines from offering to translation this page in search results.'
and it introduced a typo... So it either should be like in the patch or the translation word should be changed to translate.

Thanks
AndyB