bfsc: Hide Tools and Concepts pages

These pages are too complicated. We drop them for now, but
only by hiding them.
bfsc: Home page, fix link to hidden pages
bfsc: modify color scheme (bg white)

Make the background of the main text area white in order
not to make the score examples awkward.

Instead make the remaining page background light blue
bfsc: Make menu items bold
bfsc: Examples: Remove inconsistent page heading
bfsc: Examples: Reword introductory paragraph
bfsc: Examples: Remove links to subpages

The subpage structure is currently hidden (and may possibly be removed
completely later).
bfsc: Examples: Reword Automated Engraving

I think this is _much_ more teasing and pleasing and elegant than before.
bfsc: Add Beethoven-Henle example files
bfsc: Add Berg example files (WIP!!!)

This example contains several errors that have to be fixed,
but I don't have the materials at hand right now.
bfsc: Add Estrella example files
bfsc: Add fried example files (for Examples page)
bfsc: Add eja-mater PNG file

The PDF had already been added earlier
bfsc: Add Variations-and-theme example files
bfsc: Examples: Include example images
bfsc: Examples: Use template w/o subpages

Effectively hide the subpages.
Maybe we'll restore the structure later, but for now this one-page
solution seems very nice.
bfsc: Consulting: Make intro more streamlined
bfsc: Consulting: Clean up "Analysis"
bfsc: Consulting: Clean up "Software set-up"
bfsc: Consulting: Reword "Training, mentoring"