fixup BitmapIntegrationTest testcase

fixup testSaveLoadedImage Test in MenuFileIntegrateionTest

added write permission to test manifest
removed createNewFile() for load test

fixed bitmapIntegration centerBitmap test

added wait to stampTool button test
Merge pull request #201 from Catrobat/fixup_test

fixup BitmapIntegrationTest testcase
accepted: @X4mp [ru]