Update module to use Drupal 8 Compatible entities

We should utilize Drupal 8 compatible entities for tracking events/activities.

Outline for feature:

• Create a entity type for Activity.
• Ensure that we exclude this entity type from the Activity module's list of trackable entities.
• Activity Templates will be a Plugin based Bundle off of the Activity Entity Type. Allowing us to extend trackable things

The D8 branch has several other issues, most notable happens while we are utilizing it with views.