* Add a tutorial step about the new existing users feature (step 3)
* Move the corresponding feature request to 'implemented' and modify it a bit
* Rename step 2 to "Rally input task format"
* Add tables of contents to the lessons
* Other fixes that make docs more precise
Change-Id: Ic800fdfa3df883f267ddcae2165f804c11699bd0
b5142f1a01