Don't hide old Association reuses

[Matthias Schoettle]

Old reuses of association, i.e., not done using a feature selection on an association end, are automatically hidden. It is therefore not possible to remove or update them.

I suggest to only hide association reuses if they have a feature selection associated.

Steps to reproduce:

• Open Workflow concern
• Open Workflow aspect
• ControlFlowNode has a hidden operation which is due to association being reused

[Céline Bensoussan]

Temporary since the concerns will all be updated soon. To unhide it, update the code here:

https://bitbucket.org/mcgillram/touchram/src/2449b25c5fb5f7df6f278feb2fbe2c12d42617c3/ca.mcgill.sel.ram.gui/src/ca/mcgill/sel/ram/ui/views/structural/InstantiationsContainerView.java?fileviewer=file-view-default#InstantiationsContainerView.java-335