HazEmulator: add unit tests

fix start date

sphinx configuration adapted

(cherry picked from commit 081167b)

adapt contribution steps

The starting point should be the develop branch.

(cherry picked from commit 69caf56)

new translation of San Salvador adaptation study to Spanish.

new contributing author

update version number for release

update development version

Merge branch 'master' of https://github.com/CLIMADA-project/climada_p…

…ython