fixes Brick looking different on some devices

fixes #295 by lifting the 9.png left-bottom-border pixel up.

Devices which will be (at least) fixed are:
 * Nexus S (4.1.2)
 * Nexus 7 (4.2.2 - 2012 Edition)
Merge pull request #622 from Catrobat/fixed9png

fixes Brick looking different on some devices