Fixing EXRImageReader canRead to accept scanline images.

No idea why it didn't in the first place. I left the check for "" because I don't know why it was there...
Disabling Nuke DeepImageReader test.

Executing a DeepWrite in command line mode was causing a seg fault, preventing the other tests from running. I've submitted a bug to the Foundry (Ticket#2014061310000018) with a simple repro that does not use Cortex. We can re-enable the test if they fix the crash.

I also renamed the test deep exr file, because Nuke's DeepRead didn't like the .dexr extension.
IE config doesn't override OpenEXR paths per app.

Since we're using 2.1.0 now, we have fully versioned sonames, and don't need to force using the natively shipped OpenEXR