Move from MongoDB to Sqlite3 backend

Short description on how to compile towards `persistent-sqlite` on Windows
from [here](https://github.com/yesodweb/yesod/issues/644):

* install `sqlite3` from official website (together with source files)
* (re-)install `persistent-sqlite` as follows:

```batch
cabal install persistent-sqlite-1.2.1
    -fsystemlib
    --extra-include-dirs="C:\Bin\sqlite3\include"
    --extra-lib-dirs="C:\Bin\sqlite3"
```

This way it's possible to overcome the issue defined by the ticket
[#7056](https://ghc.haskell.org/trac/ghc/ticket/7056) with regards
particularly to using `persistent-sqlite` as Template Haskell on Windows.

P.S. Before I made it working with `sqlte` I switched to `mongoDB` backend,
which was working on Windows (just FYI).