lib/sqlite3: intro nity interface

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
tests: add a test for the Nity sqlite3 module

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
lib/sqlite3: store and use the error code of a failed database opening

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
tests: test some errors of sqlite3

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>