additional identifier which properly disambiguates
the structure view from any other view with the same attributes. This is not an ID,
because it is possible to have many references to the same physical structure view
from different sequences in an alignment. A structureState element citing the same
viewId will appear for each instance.
unique id used by jalview to synchronize between stored and instantiated views
Tree ID added for binding tree visualization settings to vamsas document trees in jalview 2.4.1
Optional minimum colour for graduated feature colour
threshold value for graduated feature colour
threshold type for graduated feature colour