The first meeting of the Drupal User Group Bodensee (Lake Constance) in 2017 will be about migration to Drupal 8.
Drupal
The enterprise OpenSource content management system which is available for free at https://www.drupal.org where you can find all the details and also references.
Drupal has a very active community with tens of thousands of developers all around the world and they also have a huge focus on standard compliance and on security.
The Drupal 8 module Onomasticon automatically displays the definition of taxonomy terms everywhere a term is used. However, you may want to avoid self-definition on the term's own page as its description is already visible without it.
Websites can use protocol handlers to provide a convenient way for users to open default applications directly from a web page. In Drupal you can add such handlers to the list of allowed protocols, e.g. in order to create a link for your visitors to directly call you by skype.
As a team that had spend time and money for years in developing best practices for staging,
Drupal 8 projects are in most cases controlled by