[add] logger - use env for rotating log params (#1857)
[add] logger - use env for rotating log params (#1857)

Two environment variables were added to allow customization of the rotating log parameters:
- `FLEXGET_LOG_MAXBYTES` defines the maximum bytes per file (default 1 MB)
- `FLEXGET_LOG_MAXCOUNT` defines the maximum number of files (default 9)
LynxyssCZ/Flexget,tobinjt/Flexget,OmgOhnoes/Flexget,malkavi/Flexget,Danfocus/Flexget,jawilson/Flexget,Flexget/Flexget,Danfocus/Flexget,LynxyssCZ/Flexget,gazpachoking/Flexget,qk4l/Flexget,gazpachoking/Flexget,Flexget/Flexget,ianstalk/Flexget,malkavi/Flexget,OmgOhnoes/Flexget,JorisDeRieck/Flexget,crawln45/Flexget,OmgOhnoes/Flexget,malkavi/Flexget,ianstalk/Flexget,crawln45/Flexget,LynxyssCZ/Flexget,Danfocus/Flexget,tobinjt/Flexget,JorisDeRieck/Flexget,qk4l/Flexget,JorisDeRieck/Flexget,jawilson/Flexget,jawilson/Flexget,ianstalk/Flexget,LynxyssCZ/Flexget,Flexget/Flexget,malkavi/Flexget,Danfocus/Flexget,crawln45/Flexget,Flexget/Flexget,crawln45/Flexget,JorisDeRieck/Flexget,tobinjt/Flexget,qk4l/Flexget,jawilson/Flexget,tobinjt/Flexget