ffmpeg: Re-write the module (#236)

* transcribe: fix -t flag

Signed-off-by: yshalsager <[email protected]>

* ffmpeg: re-write the module

Signed-off-by: yshalsager <[email protected]>

* ffmpeg: switch to async run

Signed-off-by: yshalsager <[email protected]>

* merge with statements

* fix redefiniton of built-in function

* is_url undefined

* add del_pre

* further optimization

* lint fixes + added -d flag (to do not delete media after process done)

* minor fixes

* remove unwanted line

* Rename ffmpeg.py to ff_mpeg.py

Co-authored-by: Krishna-singhal <[email protected]>