Doc: Changed section numbers in QML basic type pages.

changed section2 to section1
changed section3 to section2
...it looks better to have a section1 because the CSS makes them
look more prominent.

Change-Id: I2e8e336dd38199adcffee1f91a16bc2fae885cfe
Task-number: QTBUG-40335
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>