Add feature for user to add a new data type from context menu when the current data type is Unknown

#194 (closed)

This MR create an item in context menu that open a dialog to select from existing data types or create a new data type for the current data set. When submitted, the new data type will be set for the data set. The info will be updated in the info box.

(To add channels to the dataset the user then can right click on each channel to add a that channel to the data set or using Channel table)

A new help document will be added later in another MR.

For testing, create the data set that has only channel not in DB. Ex: VDP from Pegasus_KCT06_Test.nan