Added SerializableReferenceService interface and implementation.
Reworked how mode transitions are referenced to allow for referenceing
mode transitions that do not have names.
Merge branch 'mode_transition_fix' of /home/git/repositories/rsesc/aadl_graphical_editor into develop
Fix for device appearance. Devices are no longer filled and reference to
style is no longer broken.  Shading is now partially transparent.
Flow source and destination indicators are now straight when used with
feature groups.