Support more types in SqliteBack. Improved SqliteBackTests.

Added sqlite backend support for:

* `set<int>`
* `set<string>`
* `list<int>`
* `list<string>`
* `map<int,double>`
* `map<int,int>`
* `map<int,string>`
* `map<string,int>`
* `map<string,double>`
* `map<string,string>`