[CDF-290] - CCC - Option "LeafContentOverflow" supports value "Visible", which should be documented.
Merge pull request #96 from dcleao/CDF-290

[CDF-290] - CCC - Option "LeafContentOverflow" supports value "Visible", which should be documented.
Removed cached fields _valueRole and _valueDim from pvc.BarAbstract
Added the ability for plot classes to register themselves under their type name.
pvc.BaseChart#_createContent now receives the parent panel as first argument.
Replacing _createPlotPanels by a mix of _createContent and base calls.
Changed existing MetricPoint chart options sizeAxisRatio, sizeAxisRatioTo, placing them in a custom size axis, and autoPaddingByDotSize  placing it in the plot options
Changed creation of plot panels into the plot classes.
Plot Panel creation is not done by Plot classes but by the chart through registered Plot Panel classes for plot types.
(NormalizedBarChart broken)
Chart is now adding plots it creates explicitly through _addPlot, instead of relying on Plot to do it
Moving _buildOptionId of Axis' derived classes to the Axis class
Moved _createContent and _createPlotPanel, in the file.
Externally created plots cannot provide options at top level. No prefix is provided for these that allows placing options at top level (actually, there is one, but a random one).
Moved setting of Panel legacy fields from the chart to the panel itself.
Animatable is now in the panel, instead of the chart and is now using the already existing interaction bitmask to register the fact.
Removed pvc.BaseChart#_trendable and now the need for a trend plot is determined in pvc.BaseChart#_addPlot.
Removed private, cached, visual role fields from the chart classes.
Moved chart registration of cartesian axes under the aliases in "v1SecondOrientedId" to the cartesian axis class.
Moved pvc.*Chart._createVisibleData to the corresponding *Plot class.
* Added _hasDataPartRole override as true to the pvc.CartesianChart class. Then, only the HeatGrid chart is overriding to false.
* Added method pvc.BaseChart#_registerInitLegendScenes to allow moving the _initLegendScenes code of the WaterfallChart to the WaterfallPlot.
* Changed the DataPart option to allow external configuration.
* Moved pvc.CategoricalChart#_getContinuousVisibleCellExtent to the CategoricalPlot class.
Changing firstDimension* uses to lastDimension* uses. On the path to visual roles with discrete dimensions and a leaf continuous dimension.