Added throttle for sending SMTP messages

v2.1

Update README.md

Updated and tested with Jetpack 4.6.3 [L4T 32.7.3]

• Can now configure separate streams for AI and recording:
  My three $20 IP cameras from ALI express work fine using QVGA / Best / 10 fps / VBR / I Frame 1 and H.265 / 720P / Best / 25 fps / VBR / I Frame 1. There is plenty CPU and GPU bandwidth left to add more cameras.

• Removed use of 0 copy shared memory as not applicable to python, just produces loads of error logging.

• Changed default logging of NVidia APIs to error only.

• Fixed error in startup script creation when using a config file from outside main directory.

• Made logging a bit more human readable.