Markup and escape should be imported from markupsafe

[davidism]

These were still left over from Jinja's early days. Noticed they were still exported and documented, so now the Jinja versions show deprecation warnings pointing to markupsafe.

[CarliJoy]

I used this in paragraphs in #1386 to describe how and when to use env.get_markup_class

Also I used it to refer to the Markup class as link.
The external link didn't work.
So I kindly ask if you could fix the merge conflict #1386 cause I am kind out of ideas considering this change...

[CarliJoy]

The problem is also that now the explaination of what Markup does and what the .__html__ means is out of the documentation.
And I kind of referred to it in other parts of the Jinja documentation. Now it is all a bit loose an and unconnected :-/

The supposed links to Markup (i.e. in the current explanation of the parameter does not work.