Refactoring and clean-up of core classes and interfaces

Conflicts:
	src/ch/uzh/ifi/attempto/acewiki/aceowl/ACESentence.java
	src/ch/uzh/ifi/attempto/acewiki/core/AbstractSentence.java
	src/ch/uzh/ifi/attempto/acewiki/core/MonolingualSentence.java
	src/ch/uzh/ifi/attempto/acewiki/core/MultilingualSentence.java
	src/ch/uzh/ifi/attempto/acewiki/core/Sentence.java
	src/ch/uzh/ifi/attempto/acewiki/gfservice/GFDeclaration.java
	src/ch/uzh/ifi/attempto/acewiki/gui/SentenceComponent.java
	src/ch/uzh/ifi/attempto/acewiki/gui/TextRow.java
	src/ch/uzh/ifi/attempto/acewiki/gui/TranslationsPage.java