Add author names to about menu

Adds a file containing the author information in zenodo metadata format (see https://developers.zenodo.org/#representation), this file is used to add the author names to the about menu. In this step also the about menu is moved to a separate ui file for easier editing.

The new about menu looks like this:

ToDo:

• get ORCID from everyone who wants to provide it

Closes #52 (closed)