removed profile_url field from instructor table in database (since instructor's profile URL is created using 'id_from_json' field in the same table)
Changelog:

1. Moved call to add_provider() to create_database() because add_provider() should only run when the database is created for the very first time.

2. Replaced Connection object with Cursor object in add_courses() and add_university() parameters.

3. Modified the query in add_instructor() as needed by edit done in previous commit.

4. Added listjson_new_data() and list2json_new_univs() that finds new entries in Coursera's list.json (https://d1hpa2gdx2lr6r.cloudfront.net/maestro/api/topic/list) and list2.json (https://d1hpa2gdx2lr6r.cloudfront.net/maestro/api/topic/list2) respectively.

5. Renamed coursera_course_table() and coursera_university_table to new_coursera_courses() and new_coursera_university() to make them easier to comprehend.

6. Made changes in coursera() correponding to other edits in this commit.