Support style classes in DataTable rows and cells

[zkauker]

In many cases make sense to add CSS classes to table TRs and/or TDs - especially if the style class should be determined by the contained data (example: in a todo list highlight the rows which have high priority)

[gabor-farkas]

Things are a bit difficult. BaseComponent contains many model fields and builder methods that provide basic functionality that can apply to any html element, but we cannot make everything a BaseComponent because that'd boost memory footprint quite a lot in case of a datatable for example. Now that we need a "part" of basecomponent functionality for table rows and cells, we have to use composition instead of inheritance.

Model

• add a styleclasses list in DataTableCellModel and DataTableRowModel. It should be null by default. Create a HasStyleClasses interface and BaseComponentModel should also implement that (with the getter and setter).

  Builder

• create a StyleClassesBuilder class that takes a HasStyleClasses as a constructor parameter and provides addStyleClass, bindStyleClassPresent, removeStyleClass, as seen in BaseComponent. Create an instance of this class in BaseComponent and make the above three methods delegates to this styleclassesbuilder instance.
• ... the way to use this builder for cells and rows is yet to be defined.

  Renderer

• based on the styleClasses listener in BaseComponentRenderer, create an individual class called StyleClassesRenderer that takes the list binding as the first and the JQuery widget as the second constructor parameter.
• make it implement the ListenerRegistration interface, so that it can be disposed.
• use these classes in the renderRow method in DataTableRenderer
• make sure to properly dispose listeners

... to be defined.