Implement a warning popup when the user changes the type of a column that has been already populated.

To be done/merged after DROOLS-3051.

Acceptance criteria

• If the column contains no value, no confirmation is needed
• If old and new types are the same the user has to decide if the values should be removed or not
• If old and new types are not the same the user has to accept that old values will be removed
• All warning popups should contains also a "Cancel" command to abort the edit
• If the user try to update the column type with the same column type no warning should be raised and data should stay untouched