Checklist from Hiring to Onboarding

Merged Ernst van Nierop requested to merge hb-onboarding-2015-08-03 into master

Removed checklist from Hiring. Added it to Onboarding, and added many items to the checklist. MR !859 (merged) needs to precede the current request, which is why I used the WIP label.

\cc @slykahn FYI, and please review new checklist.