Sqlite DB not vacuumed

[cbeaujoin-stellar]

The sqlite db should be vacuumed.
At shutdown for example.

[eht16]

Just implemented it and released in 2.7.0.

I was struggling with this for a long time and not sure how to implement it best. I think at shutdown is probably good.
Note that it is configurable and disabled by default, at least for now.
To enable it, set constants.DATABASE_VACUUM_ON_SHUTDOWN to True.

[cbeaujoin-stellar]

Hi Enrico,
thank you for the improvment