add a Lang meta into the each article and set DEFAULT_LANG setting
which is 'en' by default.
Than, only articles in the default language (or without variant in
default language) will be shown in the index of the blog. And each
Article will have translations list.
The same is applicable to the static Pages.
Also, separate feeds are generated for each language except default.
Added some more notes about how this is working on the documentation. I do think
that the overall structure is clearer now, and easiest to understand. After all,
that's how it should always be !
--HG--
rename : pelican/processors.py => pelican/generators.py
rename : pelican/generators.py => pelican/writers.py
