Fall detection (#237)

* Initial version of fall detector learner with naive fall detection implementation

* Added alternative ways to retrieve data from Keypoint, similar to Pose class

* Formatted imports

* Initial version of fall detection demo and empty README

* Reverted changes in target.py for Keypoint class

* Reverted to default Keypoint.data access and fixed download path

* Added convenience __getitem__ method and properties for accessing Keypoint data.

* Fall detection evaluation on UR Fall Dataset WIP

* Improved reading of UR Fall Dataset and completed basic evaluation

* Inference demo to run fall detection on predetermined images

* Renamed fall_detection.py to webcam_demo.py

* Webcam demo cleanup

* Removed unused time import

* Infer now returns a list of detections

* Inference demo now works with modified learner for multiple poses

* Infer now returns the pose as well

* Inference demo works on multiple detections and prints appropriate messages and graphics

* Webcam demo now works with multiple fall detections

* Some modifications to the eval method and a docstring with some explanations.

* Evaluation demo

* Changed the way naive fall detection calculates angles for major increase in sensitivity and minor decrease in specificity

* Changed the way naive fall detection calculates leg position, avoiding some false positives and fixed minor bug

* Added condition for calves angle, increasing sensitivity significantly

* Added tests for fall detector

* Added download method and did extensive changes all around to work with tests

* Finalized inference demo with images downloaded from FTP

* Finalized eval demo with image download from FTP and argparse

* Finalized webcam demo

* Added fall detection demo readme

* Added NotImplementedError on fit and made some methods private

* Added documentation for fall detector

* Minor fixes

* Added tutorial notebook and updated README

* Update tests_suite.yml

Added fall detection tests

* Added missing references on fall detection tests

* Fixes according to review

* Couple of fixes based on review

* Added fall detection on packages.txt

* Added a dependencies.ini for fall-detection

* Removed notes section

* Update dep installation

* Added changelog entry for fall detection tool

* Added fall detection node

* Added fall detection node instructions

* Added Fall Detection entry in list of nodes

* Added python ros node for fall detection

* Review fixes

* Temporary test

* Revert "Temporary test"

This reverts commit 40dba12da1d5adc447bb570b94dab81e73794e1f.

Co-authored-by: ad-daniel <44834743+ad-daniel@users.noreply.github.com>
Co-authored-by: Nikolaos Passalis <passalis@users.noreply.github.com>
Co-authored-by: ad-daniel <daniel.dias@epfl.ch>