`io_counters` is not always available (e.g. under Ubunutu 20 run in WSL), resulting in an exception being throw.
See #1373 for a complete explanation of the issue.
* do not rely on the ordering of the json entries, as it can vary from
one version to another.
* ensure variables are always initialized (even in case of exception)
* add some debug logging on errors in nvidia-smi parsing
* signal can only be used in the main thread, leading to an error when StatisticThread is instantiated inside a QThread
* misc fixes on imports and variable names
* Add chunk notion for parallelization
* Allows Node desc to implement custom updateInternals
* CameraInit node implement a specific updateInternals to update the
input image list
* FeatureExtraction, FeatureMatching, DepthMap, DepthMapFilter:
implement parallelization
