Lesson 1 Update

[cvoky]

Added tidyverse, shiny intro + homework

[ex-man]

there is a small bug on my machine: we can resolve later.

What is more important, the pull request still contains the following "bugs"":

• [ ] tables are showing ratios and not absolute numbers
• [ ] there is the overall tab, that is redundant
• [ ] filtering latest year not implemented, but this may be an exercise for the students (otherwise the data is misleading) => For lesson3, let's start by discounting the losses first and looking at what it does => overall UWR over 5 years discounted (this should be exercise 0)

Accepting the pull request, so that others are not blocked, but @cvoky, please look at this...