Doc(all scope): Refactor docs.

Add unit test model.

Solve SQL injection problems.

Fixed some bugs.

Refatored code and fixed some bug and typo.

Fix some bug and bring database file to user folder(~/smartpet.db).

Deleted commented code and added some comment.

Fixed bug.

Used more simple and short code to refactored the code in web api.

Changed the database controlling functions because it needs to adapt …

…other functions.