Use shinyFiles

- they don't get installed as proper vignettes by install_github anyway

- better build the pkgdown website and browse online

- fixes #16

- More flexible input: Detect field and decimal separators.

- fixes #15

- Also, add tests for distance_map()

- fixes #14

- fix hardcoded CMR example

- so that it gets installed

fixes #13

- even if not interactive, since sometimes I call mapMCDA_app from a scripted separate process

- So it matches the classification exported to csv

- otherwise, level labels get exported as strings of the form (a, b].

- also, fix example