Handle the 'real' datatype correctly in the SQLite driver

Handle the 'real' datatype correctly in the SQLite driver

The 'real' datatype should be seen as a QVariant::Double type and not as
a QVariant::String type otherwise it does not get presented correctly
when using a non Qt application to access it.

Test is included for QSqlQuery.

Task-number: QTBUG-16373

Change-Id: Ie323ce49eb95e4d6bb4c3814ba9a957a63f4b259
Reviewed-by: Yunqiao Yin <charles.yin@nokia.com>
(cherry picked from commit b23631015c23a49e3b4d296ea0a6266bfce3d4f1)
Reviewed-by: Mark Brand <mabrand@mabrand.nl>