Click and change the filter name in the completion list prevents it to be added to the pipeline

[Mario Ceresa]

Editing a filter name in the completion list, converts it to unicode and prevents the proper creation of the wrapping class with error:

templates_dict[f] = type(titk_name+"Data", (FilterData, ), traits_dict)
TypeError: type() argument 1 must be string, not unicode

It could be fixed with a call to str() for the first argument of type() but editing the completion list does not make any sense as the list is directly taken from WrapITK. So probably the correct fix is turn the list to read only