DataSet-Editor: Validation messages of "Computed Columns" and "Parameters" starting with "&"

[speckyspooky]

The wizard for the datasets shows a "&"-sign at the beginning of the validation messages.
The shown "ampersand" appears due to the creation of the validation messages which use the lable name directly
and not recognize that some labels use the "ampersand" for the eclipse-shortcuts.

Some examples for the validation messages:

Additional on it the messages shows different usage of "can not" and "cannot".

I will create a PR to remove the "ampersand" of the validation message and change the messages to the usage of "cannot" (instead of "can not").