[tutorials] one by one

[stonier]

• [x] tutorial one - data gathering, #23, #24
• [x] tutorial two - battery check, #24, 074b52dc
• [x] tutorial three - blackboards, #25
• [x] tutorial four - introspecting the tree, #26
• [x] tutorial five - action clients, #27
• [x] tutorial six - context switching, #28
• [x] tutorial seven - docking, cancelling and failing, #29
• [x] tutorial eight - dynamic job handling, #32
• [ ] tutorial nine - bagging