Bug 396793 - Text decorators

*Added contribution by Andreas to draw text decorators
*Added missing interface ITextDecorator and TextDecorator class
*Added bounds calculation
*Added disposal of text decorator fonts
*Added test (UI)
*Added support in Sketch tool for manual testing
*Added support for setting foreground and background colors in text
decorators


Conflicts:
	plugins/org.eclipse.graphiti.ui/src/org/eclipse/graphiti/ui/internal/parts/PictogramElementDelegate.java
	tests/org.eclipse.graphiti.bot.tests/src/org/eclipse/graphiti/bot/tests/GFInteractionComponentTests.java
	tests/org.eclipse.graphiti.testtool.sketch/src/org/eclipse/graphiti/testtool/sketch/SketchFeatureProvider.java
	tests/org.eclipse.graphiti.testtool.sketch/src/org/eclipse/graphiti/testtool/sketch/features/DisplayDecoratorFeature.java