Optional ColumSelectionWidget for InputMappings #48
Description
At the moment, columns are mapped to input parameters using the column name in the column input mapping. However, we would like to allow the users to select the column to operate on in the dialog, too. This will also be very, very important for the general SciJava Module execution node (different story).
In the `ScriptingNode', it would be ideal, if the person writing the script could define whether the value of a module input is grabbed from the incoming table (column selection in dialog) or set once via the UI. Of course this is not possible for every input type. For some there exist only KNIME cell types (column mapping), for some there exist input widgets only (UI only), for some there exists both.
The script writer should be able to define the desired behaviour. One suggestion is, that he uses the extra @Attr annotation of the @Parameter of SciJava, to give a hint to the UI generation (simple flag with two states). Ideally, the current ColumnInputMapping can be replaced with an UI which makes choosing the behaviour easier for the user (radio buttons/check boxes etc if from table or from ui). Additionally, we have to add WidgetModels for the column selection itself.