* QuestionGroupsDatabase.cs:
* QuestionGroupsRepositoryADO.cs: Changed id to question_group_id

* QuestionGroupsManager.cs: Changed id to question_group_id


* QuestionsDatabase.cs: Changed id to question_group_id
and id to question_id

* QuestionsManager.cs: Changed id to question_id
added method DeleteQuestions

* QuestionsRepositoryADO.cs: Changed id to question_id

* Resource.designer.cs: 

* MainActivity.cs: Added code to delete the group