[#36] support reference to homonyms in dedicated class with Javac

add ElementsWrapper interface and make method ProcessingEnvironmentWrapper#getElementUtils() return it instead of the wrapped Elements object from the compiler
add ElementsWrappers class which is a factory of ElementsWrapper
ElementsWrappers creates a Javac specific implementation that read imports from JCCompilationUnit object if avaiable, otherwise directly from the source file
rename UnresolvedReferencesScanner to ReferencesScanner which now is the only class responsible for resolving unknown references
refactor JavaxExtractorImpl to be fully dependent on result of the ReferenceScanner, it is also now not supposed to be called on a TypeElement which has missing references (will raise IllegalStateException if it so happens)
add integration test of Dedicated classes with references with classes with the same simpleName (but obviously not in the same package)
now store unresolved references as Element instead of DAType in ParsingResult, saves unnecessary parsing and allows look up already found missing Element