Refactored Code to Resolve Implementation Code Smells

[ayushi250317]

1. Cyclomatic complexity of method processSingle present in PageModelExtractor class was 19. Reduced it to 9 by introducing two methods that handles extraction of single value and multi values from source.
2. Renamed convert methods in PageModelExtractor class for increasing code readability
3. In convertHttpClientContext method of HttpUriRequestConverter class, introducing explaining variable to simplify the complex statement : authState.update(new BasicScheme(ChallengeState.PROXY),new UsernamePasswordCredentials(proxy.getUsername()proxy.getPassword())) and increasing code readability