Repairing test cases;
Add general valid/unvalid tests for lexicons;
Added more Exception's while Parsing;
	- UnvalidLexiconException(thrown:)
		.Empty Lexicon
		.Empty Start-symbols
	- UnvalidElementaryTreeException(thrown:)
		.leaf-node, inner-node mistakes
		.beneath spine (not dominated by epsilon)
		.Empty categories/labels
		.two root nodes
		.etc
Resolved Bug in parse-tree's;