Rotate step titles to be aligned with outer border of the "circles"
Fix plural "Future works" -> "Future work"

For reference: https://owl.english.purdue.edu/owl/resource/541/02/
Fix plural in "Developing extensions" step
Update build step title to be more specific

This commit changed the title from

  All steps together

to

  Unix/Ubuntu build
  (see ReadMe for Windows and others)
Adjust step title position
Adjust gradient of outter box to have black text on a lighter background.

Changed the top color from "164271" to "6884a0".

Note that to ensure the blue color of the python logo doesn't blend
into the new lighter gradient top color, the gradient of the "middle" box
 remained untouched.
Update test output to report 100% of tests succeeded.

See http://open.cdash.org/viewTest.php?onlypassed&buildid=3397900
Add PDF generated based on SVG obtain from 39f81bb