Change LOG_DIR to absolute path and change switch log folder.

ACTUAL_LOG_DIR is relative path
On log folder change: Close old handlers, don't get extra console handler
+ some PEP8
Change to file_path

Change paths to logger.sb_log_instance.log_file_path
Use utf-8 for logfile encoding
Change logdate to numbers %Y-%m-%d to avoid foreign month abbreviations
Change format Backlog date to format Next Ep date
Change sickbeard.WEB_LOG only when log_dir or option is changed