Updated primer wording
move app to top level
add anchors for easier linking
Move j5 ref to primer page
SketchUp files for assembly diagrams
Based on SparkFun ARDX assembly diagrams
Images exported from assembly diagrams
display layout and assembly diagrams
Simplify exercise content generation - use single md file for each exercise
Highlight selected section in menu
qualify image link
Electronics primer content
still needs a few more images
Also fix menu text widths