Started work on parental guidance app handler
Implemented app default PG handler device modifier and tests
Refactoring App Deafult PG Handler tests so that showChallenge is called as expected, with an object that contains a function called 'onGuidanceChallengeResponse'
Added a check in appdefaultpghandler to ensure that guidanceChallengeResponseCallback has a function called onGuidanceChallengeResponse
Adding basepghandler file
appdefaultpghandler now extends the new basepghandler
Merge pull request #170 from fmtvp/parental_guidance_handler

Parental guidance handler