fix issue #430

this will make the Offscreen renderer use the same Viewport translation that the GUI does, as per the issue #430 

it uses the same code path for both so there should be no big differences 

it takes advantage of the 'default copy constructor' features inside of QGLView to copy a fake camera and then translate that camera for outputting the viewport information. 

the tests have been updated to pass by altering the rotations/translations used (leaving the original images without modification)

camera tests pass under clang and gcc