Write OpenFX plug-in for FileTransform

Issue #1117 requests OpenFX plug-ins for OCIO and Michael has PR #1371 in progress that is almost complete to implement a ColorSpaceTransform and DisplayViewTransform plug-in, which are the key ones. It would also be great to have a few more OpenFX plug-ins, for example for FileTransform. This would allow people to apply stand-alone LUTs in any of the formats OCIO supports, including the Academy/ASC Common LUT Format (CLF). The implementation should include an "invert" toggle button, similar to Michael's work.

It would also be great to have OpenFX plug-ins for LookTransform and NamedTransform, although these could also be in separate PRs.

Beginne mit Issue #1117 und PR #1371, die den bestehenden OpenFX-Plug-in-Kontext für OpenColorIO bereitstellen. Ermittle, wie das FileTransform-Plug-in neben der Arbeit an ColorSpaceTransform und DisplayViewTransform eingeordnet werden sollte, einschließlich des Invert-Toggles. Die Aufgabe ist erfüllt, wenn ein FileTransform-OpenFX-Plug-in unterstützte eigenständige LUT-Formate einschließlich CLF anwenden kann; LookTransform und NamedTransform gehören zu einem separaten Folgeumfang.

Vom Indexierungsmodell aus dem Issue-Text verfasst.