Sqlite: Improve constraint support

Now you can add more than one constraint. And we added some
new constraints too.

Change-Id: I849d2d2ef6e44c897a65ff2bdfe8d172a345c991
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

tests/unit/unittest/sqlitedatabasebackend-test.cpp

@@ -39,7 +39,7 @@ namespace {
 using Backend = Sqlite::DatabaseBackend;
 
 using Sqlite::ColumnType;
-using Sqlite::Contraint;
+using Sqlite::ConstraintType;
 using Sqlite::JournalMode;
 using Sqlite::OpenMode;
 using Sqlite::TextEncoding;