final patches

- Fixed issue where removing and recreating pm2 processes resulted in pm2 ID changing after some time. Script now uses the process name even if the user configures it using process ID. -  (does require you to go through configuration again to avoid this issue)
- Fixed issue where running the script from within the bot folder resulted in profittrailer.jar being deleted. 
- script can be run without having to cd to the correct directory (i.e /var/opt/linux-update.sh is fine)
- Script will self update now. (note that if you are updating to a version which does not come with the updated script you will be downgrading the config and need to manually upgrade again)
- Cleaned up code. Deleted a bunch of lines simplifying duplicate sections
- fixed inability to handle filenames with spaces
- fixed inability to handle script name with spaces
- Automatically remove old updatescript backups (keep latest 5 only)