Refs #2626: Adds "cy_" prefix (namespace) to property names. Internal ControlPoint object no longer exposed to third party clients (just a simple Map of position->color now). "Item Labels" renamed to "Value Labels".

(cherry picked from commit bce146fd3b5a2efda32bb2cecad9b5cee38c283a)
Refs #2626: Fixes bug that makes Heat Strip bars disappear if single value column is null and axis range is not network-wide.

(cherry picked from commit 59576f7b08857f46fe91cff82492a1b71bde964a)
Refs #2626: Fixes bug that prevents charts from being updated right away after related column or row value changes (also affects updating visual mappings).

(cherry picked from commit 7298059b3bc79782ab2ac613188592681fba4c21)
Refs #2626: Replaces gradient property "cy_stopList" (which was a Map) by properties "cy_gradientFractions" and "cy_gradientColors" (arrays), so duplicate fractions can be saved, even if only distinct values can be set to the AWT Gradient Paint. It also simplifies the serialization. Chart property "cy_range" is now a primitive double array, in order to avoid null values.

(cherry picked from commit cd423a7dcd4318561606071dc216483483583a52)
Refs #2626: Fixes converting internal Enum properties to simple strings. Adds unit tests for chart/gradient properties.

(cherry picked from commit 7f1472bc44072b03d440dc55581698951554f20e)
Refs #2626: Changes Array-typed charts/gradients properties to type List, in order to keep it consistent for app writers. Fixes bug that prevented chart editors from being reset properly after removing a custom graphics.

(cherry picked from commit 9051f59170baa9233947167a5d2f4469ca8a4418)