IGBF-201 - add method for renaming joined graphs

Modified the combine graph and split graph actions to trigger a refesh of the Data Management Table.

Added a container (a list called comboTrackStyles) to the DataManagementTableModel to store styles for joined graphs, even though those styles do not correspond to exactly one feature.

Modifiy DataManagementTable and DataManagementTableModel so that the Data Management Table shows a row for each DataSet that is associated with a style (just like before) and then additional rows are displayed for joined graphs. Methods in both .java files had to be modified to accomodate the SimpleTrackStyle class for the style, in most cases this was done by changing the type from the TrackStyle class to the ITrackStyleExtended interface. Anywhere where getMethodName was called on the style, it had to handle the possibility of getting a null value. The biggest change is that methods in both classes have to allow for the possibility that a given row may have style but now a feature. This is the case for joined graphs, which are represented by a single style, but that style is not associeated with exactly one feature. (feature is the turm used for the DataSet object). This has the end result of putting joined graphs in the Data Management Table, thus creating a place to edit the joined graph name.

Making this method 'synchronized' removed problems. IGBF-201

Update comments and method name (formerly generateFeature2StyleReference) to be clearer.