Improve behaviour of back/forward buttons in OMEdit Documentation browser

[Francesco Casella]

The yellow back and forward buttons in the Doumentation browser are very useful to navigate the hyperlinks in the HTML documentation. However, when they are pressed, they bring into view the previous or successive window from the top of the page. In case the documentation is longer than one page, one has to scroll down and search for the line where the link was located in order to continue reading, which is extremely annoying if you do it more than once or twice.

I would recommend to record the position of the viewport on the document when hyperlinks are clicked, so that one is brought back to the same exact point when the back or forward button is clicked.

As a test case, you can take the Modelica.UsersGuide.Overview info, click on the StateGraph link, then click on the back button.