Some method renaming in TypeChecker visitor
Changed ConditionBlock to be a super class
Splitted ConditionBlock to IfThen, IfThenElse child classes
Changed StatementChecker visitor interface to reflect changes
Implemented changes in StatementChecker visitor
Changed Grammer to reflect changes with ConditionBlock
Changed StatementParserChecker unit test super class to reflect changes
Renamed methods in ConditionBlock statement checker unit test