Robustness chapter updates

[abogdanoski]

• paragraph 5 says that robustness is assessed at the claim level -- should this be mentioned earlier in the chapter? @fhoces please confirm
• It’s a bit unclear where “entry id” comes from, though it seems that it’s simply the order in which the analytic choice is recorded @fhoces - write instructions
• 4.2 remove leftover comment “[should this be “robustness check” instead?]”
• What does the mapping database look like on the platform? @fhoces - add instructions