adding sqlite::endr, and ability to give functions to database_binder

[bstarynk]

We add the ability to force the end of a prepared statement with endr and the ability to give functions to them.

[zauguin]

@bstarynk Have you seen the ++ operator? Your ppsi << "zero" << 0 << endr; can be written today as (ppsi << "zero" << 0)++;