Fitting: changing CSA definition clashes with Connect Parameter

Created by: wfranssen

After connecting a CSA parameter, changing CSA definition is still allowed, but leads to an error. Moreover, what should happen if the value it connects to changes definition?

Possible fix could be to block definition change if a Connect Parameter is active somewhere. And additionally allow only one definition shared by all data tabs? (Traces are handled in this way already.)

When forcing one definition for all data, we might restrict the user in linking parameters. I cannot think of a good reason to connect parameters from different CSA definitions. But who knows...

The issue of course occurs for all fitting routines where definition changes are possible.