New features

- Added demo content generators for nodes and menus. Check "drush list | grep demo" to get a list of possible demo content commands. Drupal console support is also included.
- Implemented the Link Attributes Drupal module.

Added Bitlink API Service which can be used by custom modules to programmatically generate and expand Bitly URLs.

Changelog:
* 1629a47 Issue #2992439 by radimklaska, kyberman: Optional "e-mail wall" [Radim Klaska radim@klaska.net]
* 4563b8c Issue #2997331 by puch147: Challenge not showing. [Jean Valverde moimog33@gmail.com]
* 8fa41f1 Issue #2938174 by volkswagenchick: Add Readme. [Jean Valverde jeanvalverde@catalyst.net.nz]

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Small update mainly for PHP 7.2 compatibility.