Propagate Campaign Tag to Activities Associated with a Project

Adding a project to a campaign should result in associated activities being added to the campaign as well.

There are two scenarios we are interested in here:

1. A project is created and tagged with Campaign X. Later, activities are created within this project. These new activities should also be tagged with Campaign X.
2. A project is created. It may or may not have been tagged with a campaign. Activities are created within this project. Later, the project is tagged with Campaign X. All the associated activities should be updated with the new Campaign value.