Allow ImageView to accept textures with arbitrary texture coordinates

[adielfernandez]

Just needs a minor tweak to the shader in the draw() call. However, the shader would need to be made non-static.

Maybe better to make an ImageView_ARB class that inherits from ImageView and uses its own static shader with an override to the draw method?

[benjaminbojko]

I wonder if this is still an issue with the latest ImageView currently on develop. It uses Cinder's internal gl::draw() again instead of a custom shader and includes other simplifications. Needs testing.

[adielfernandez]

Good point, will test later and report back.