not limitKps inside Feature2D::generateKeypoints when using pyDetector

[hellovuong]

This only happens with SuperPoint. Rtabmap will limit key points if exceeds the limit set by Kp/MaxFeatures THEN it will generate descriptors based on extracted key points. It will work classic Features Extraction method. However, SuperPoint will generate key points and descriptors at the same time, if the limit key points method calls inside the extract key point method it will lead to a mismatched number of key points and descriptors later when the generate descriptor method calls. It is solved by ignoring the limit key points method inside the generate key point method and only limiting key points after generating the descriptors if necessary.

[hellovuong]

Sorry, there is a wrong pull. I will fix it soon! FIXED

[matlabbe]

Good catch. I'll merge it now as it can cause errors, but I opened a new issue #1225 to think about supporting that feature for PyDetector. Without this patch, the workaround would be to set Vis/MaxFeatures=0 and limit the keypoints/descriptors inside the python file. For the visual word dictionary, Kp/MaxFeatures should still work as expected.