don't flip 2D textures on load, required for texelFetch

[agreppin]

• display them as FlippedTexture in UI / objects preview
• check shader program link status

[agreppin]

Here is a minimal example using texelFetch.
texelFetch uses texture space coordinates to access pixels [0, size-1].

As of SHADERed 1.5.4, the logic of the texture VFlip feature is not clear. When using texelFetch in a shader, I must enable the VFlip checkbox, but the texture preview is now inverted ... which is confusing.

Attachment: quad0.zip
PS: please read this dicussion: How do you deal with images being inverted?