We really only need to fix the name for the activity

Tweaking the page names is only going to be annoying.
Check that the new activity name isn't too long

Adding "Copy of " to the title string can sometimes make it longer than we allow, thus blocking saving of the new activity. [#49085561]
Controller action for duplicating activities.

[#49085561]
Add "copy" link to activity index

[#49085561]