Refs #2626: Adds CyChart and other related interfaces.
Refs #2626: Adds getProperties method to CyChart interface and changes a CyChartFactory builder method so one chart's properties can be reused in a new chart.
Refs #2626: Adds Java2DLayer interface so the Network View renderer's Graphics2D object can be passed to Custom Graphics.
Refs #2626: Adds CyGradient API.
Refs #2626: Adds MappableVisualPropertyValue interface to make it easier to update CyCharts when referenced CyColumns change.
Refs #2626: Adds LockedValuesSetEvent to make it easier to update CyCharts set as bypass when referenced columns change.
Refs #2626: Renames Java2DLayer interface to Cy2DGraphicLayer. Adds Shape parameter to Cy2DGraphicLayer.draw.
Refs #2626: Merge branch 'feature/node-charts' into develop:
   Adds CyChart/CyGradient API.
   Adds Cy2DGraphicLayer so the Network View renderer's Graphics2D object can be passed to Custom Graphics.
   Adds MappableVisualPropertyValue interface to make it easier to update CyCharts when referenced CyColumns change.
   Adds LockedValueSetEvent to make it easier to update CyCharts set as bypass when referenced columns change.