Allow VRImage to EXR converter tool to also open EXR

[HenrikBC]

I'd like for the VRImage to EXR converter tool to be able to open EXR as well as VRImage files.
This way it would be useful as a tool for extracting specific channels and/or converting them to different compression types, but from EXR sources as well as VRImage files.

[matanov]

Logged as VMAX-11792. We'll try to squeeze it in some of the next releases.

[HenrikBC]

That's great news - thank you!