#742 SBE course: finalized first version (only 5 modules, other improvements)

• This finalizes the first version of the SBE course. It closes issue #742 (closed).
• Best to review per commit.
• SBE course changes:
  • There are only 5 modules, not 6 modules anymore. There is also only one case, not two cases.
  • Some textual improvements to course home page.
  • Added an extra sentence to Module 1.6.
  • Fixed typo in Module 5.1.
  • Add Module 5.8, to conclude the course.
  • Improved the water lock SVG visualization/interaction:
    • Various image layout/alignment/shapes/etc improvements/fixes.
    • All clickable image elements are now a group with background and text (both are clickable). This was partly already the case for the window buttons, but not consistently for all window buttons. Furthermore, the 'x' close buttons now also have a background, making them easier to click.
    • Fixed SVG 'transform' warnings in water lock case simulation models (due to #1021).
    • Fixes/improvements in water lock case for Module 5 (assignments related to SVG visualization).
• Moved some CSS styling from SBE course to ESCET website (affects ESCET website styling, not SBE course styling):
  • Improves code and pre styling on ESCET download and legal pages.
  • ESCET website doesn't yet use kbd, nor active menu items.
  • Adapted ESCET website pages for footer style changes. Page footers are now always at the bottom of the page, also if the page isn't fully filled with content. The page footer changes cause slightly more vertical spacing above the footer.

Closes #742 (closed)