Queries constructor Null safety

1. fact_browser
2. queries
3. Queries
4. Queries constructor

Queries class

1. Constructors
2. Queries
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Static methods
12. createStatement
13. deleteFact
14. getCurrentUser
15. getnNewestStatements
16. getStatement
17. login
18. searchStatements
19. updateStatement