Replace colors with variable (fix #45), fix format

Add interpreter and cleanup imports + carriage returns

1) Added interpreter #!/usr/bin/python3 to allow for running as ./PVEDiscordDark.py
2) Remove redundant import of os after sys
3) Cleaned up carriage return characters ^M from file to resolve the following error: -bash: ./PVEDiscordDark.py: /usr/bin/python3^M: bad interpreter: No such file or directory

Fixes #34 and any other issue that might be related to this.

Patch createWidget to root out white background-color properties instead of overriding functions. Also fixes #33

Fixes #26

fixed script not working on Python Version below 3.6

Remove previews