Installation issues

[wuxiaohua1011]

1. OpenCV Packages not found
   Could not find a version that satisfies the requirement opencv-python==4.2.0.32 (from -r requirements.txt (line 3)) (from versions: 3.4.10.37, 3.4.11.39, 3.4.11.41, 4.3.0.38, 4.4.0.40, 4.4.0.42)
   No matching distribution found for opencv-python==4.2.0.32 (from -r requirements.txt (line 3))

remove opencv dependencies since JetPack 4.4 comes with OpenCV with GPU enabled.

2. ModuleNotFoundError: No module named 'prettytable'
   add prettytable==0.7.2 as dependencies

3. pyrealsense not found with pip install

add pyrealsense2-aarch64 instead of the usual pyrealsense2 for jetson aarch64 architecture

4. add installtation of pyserial package