Internal improvements

[Dnyarri]

Almost no changes visible to user (except for some minimal GUI reactions improvement) yet some valuable internal changes like reduced memory usage for "Averager" ("POV-Ray Thread" is not supposed to work with large images anyway). From developer point of view, modules got changed so that many functions became private and aren't making a mess with "help" and docs anymore.

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This discussion was created from the release Internal improvements.