Modularize parser component

This build made some refactoring on the structure of the project so that Parser Component has a clearer API now. The other components can communicate with Parser Component by the ParserService Interface. The clients of Parser Component do not need to bother how to manipulate different parts of the parser to finish a task now, what the other components need to do is providing the input to appropriate port of the ParserService instance, and then the desired output will be returned. The clients who use Parser Service can put new requirements on Parser Component by adding methods in ParserService Interface. 
@owolabileg  @pdaian  @yzhang90 Please review.
 
Even though there is only one implementation at the current stage, I think it is still cleaner to present interfaces of components to programmers. The interface designers can make decisions in high level about the functionality of components and how different components communicate. Then the designers can change the interface accordingly and let coders implement according to the updated interfaces.