Issue #3183288 by quondam, timotej-pl, Scott Weston, themodularlab: Replace calls to \Drupal with Dependency Injection

Replace calls to \Drupal with Dependency Injection

This task is a breakaway from the existing Drupal coding standards effort. While technically more of a best practice than a standard, all direct calls to \Drupal should be replaced with dependency injection. That will also require the TBMegaMenuBuilder class be converted into a service. Reference the patch in comment #4 on the coding standards issue, which already contains a majority of the work required to make this happen.

Also adds a gitignore to ignore files that shouldn't be committed and updates changelog with latest updates.