A "relink activity" function in addition to the "relink database" function

[bsteubing]

There is a great function which enables users to replace exchanges with exchanges from another database (right click on a database yields the option). However, when we implemented this, we directly did this at the database level, while such an implementation would also be handy simply at the activity level (thus limiting the scope of the "relink database" function to one or several activities).

[marc-vdm]

If we're implementing this, I'd like to suggest to do this on an Exchange level and to let AB just loop over all exchanges. That way we can also allow users to relink specific exchanges if they wish to do so.