Fix sprite-less sprite mode

Fix sprite-less sprite mode

Sprite performance mode is supposed to work even without sprites,
mostly for testing purposes.

Also renamed the testing variable from bloat to bypassOptimizations, and
removed it from the QML API (although it previously was hidden).

Change-Id: I436554d4ee2ed3a1770839b28aba8d8ef843469a
Reviewed-by: Martin Jones <martin.jones@nokia.com>