Review of draft chapter 1: Getting started

[edward-burn]

@Braventos @KimLopezGuell could you please review Chapter 1, which gives a general introduction to working with databases from R (nothing specific to omop). As well as generally seeing if it makes sense and if there is anything you would add/ change, can you also please check that the code examples run for you?

[catalamarti]

I like chapter 1, maybe I would delete some explicit references to the database, would you be happy if i prepare a PR? @edward-burn :)