Major refactor : testing some stuff before a release

• Refactored the Style so that most of the float values (radius and the likes) have become class-attributes instead.
• Many more constructors available. Basic float properties (radius and the likes) are now integrated in the constructors.
• PieMenuSuggestedClickListener renamed to PieMenuClickListener and is now added by default. A setter is provided to change this ClickListener to a custom one.
• Added callbacks for mouse-over. Added the corresponding hoveredChildRegionColor and hoveredAndSelectedChildRegionColor to the PieMenuStyle.
• Added highlightedChildRegionColor in the PieMenuStyle.
• The PieMenuClickListener now triggers a highlight on touchDown rather than waiting for the mouse to move after the initial click.
• The complementary callbacks (highlight and hover) are now regrouped within PieMenuAdditionalChangeListener.
• HighlightChangeListener renamed to PieMenuHighlightChangeListener and now extends EventListener. Removed the associated getter and setter: now addListener() should be used for that too.
• Widgets now start with their visibility set to true (it used to be false): this is to remain closer to scene2d's expected behavior.
• Changed the Actor-sizing algorithm (and thus fixed it for low innerRadius values).
• Integrated the propagation of the alpha from parent to children. Use the setGlobalAlphaMultiplier(float) method to do so.
• Fix for Widgets contained within a Table.
• Fix of the PieMenuStyle Colors-duplication.
• Style's Circumference values now include the innerRadius value.
• New API methods to allow more customization: getActorDistanceFromCenter, getEstimatedRadiusAt and adjustActorSize can be changed to be whatever you want.
• Removed from the API the @Deprecated methods which should have been implemented by the users themselves anyway. This is reflected in the corresponding code-examples.