Missing feature detectors/descriptors/adapters in OpenCV 3

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While transitioning my code to OpenCV 3, I noticed that several feature detectors/descriptors/adaptors are missing from OpenCV 3. Some of those are:

• DenseFeatureDetector
• OpponentColorDescriptorExtractor
• GridAdaptedFeatureDetector
• DynamicAdaptedFeatureDetector
• PyramidAdaptedFeatureDetector
• plus all AdjusterAdapter

I didn't see any note of this in the transition guide. This is especially frustrating, as the transition guide has a code example where the GridAdaptedFeatureDetector is used in the v2.4 code and just disappears in the "equivalent" v3.0 code. The culprit seems to be commit 31df47b.

While I see that some functionality I can easily re-implement (such as the DenseFeatureDetector), it is still tedious to do and it was great having such a flexible feature framework. I'd like to know (1) why they were removed and (2) if it is planned to bring back some of them in future versions of OpenCV.