Add dive data members to cwShot

Added functionality to cwShot to handle dive data.

cwShot will be a catch-all class to handle all types of data, so I created an enum to handle the SurveyDataType (normal or dive).  I also added a from depth and to depth to the data as well as all associated functions (setters/getters)

There is a validator, but it should only verify that input is a double, positive depths should always be allowed.

How does it look from your end?  Once the UI bits are added, it'll be easier to test everything, but for now I only verifed compilation.  What do I need to add to cwSurveyChunk?