Based on review feedback we want to make the following changes because we do want to be able to talk about Activities and Resources (and in a separate issue introduce separate tabs for these):

1. Rename the 'Add an activity' link on the course page to 'Add an activity or resource'
2. Rename the Activity chooser title from ‘Add an activity’ to ‘Add an activity or resource’
3. Rename the 'Activities' tab to 'All'