Closes#4803
After this commit use `$titleblock$` in order to get what was contained
in `$title$` before, that is a title and subtitle rendered according to
the official rST method:
http://docutils.sourceforge.net/docs/user/rst/quickstart.html#document-title-subtitle. from
With this commit, the `$title$` and `$subtitle$` metadata are available and they
simply carry the metadata values. This opens up more possibilities in templates.
Previously we used an odd mix of 3- and 4-space indentation.
Now we use 3-space indentation, except for ordered lists,
where indentation must depend on the width of the list marker.
Closes#4563.
