English Documentation added for the latest version

English Doc is written up to the Tutorial.  First, will be looking forward to your the feedback, upon which will try to finish the doc by the end of this month.

On the original doc for ``ethna.jp`` Made one change to the ``index.rst`` i.e. added a rel link to the ``en/_build/html/index/html`` as ``.. seealso::``.

Cheers