How did this ominous file end up in my Application Support folder?
I found the culprit !

Thanks to the suggestion of @Mark Thalkman I made a DTrace script to monitor applications accessing that file. 

The application that creates the file is called AppWrapper. The way I discovered it was to look at the folders created in October in /Library/Application Support. There were only two, appWrapper and eSellerate. So I downloaded AppWrapper again and after launching it the script detected that it was accessing the file. 

I'm sure the developer made a mistake and instead of saving the file inside the appWrapper folder he saved it in ~/Library/Application Support.

For those interested, here's the script:

#!/usr/sbin/dtrace -s

\#pragma D option quiet

BEGIN
{
  printf("\n   Timestamp           gid   uid   pid  ppid execname     function           current directory file name\n\n");
}

syscall::open:entry,   
syscall::unlink:entry,  
syscall::rename:entry
/strstr(stringof(copyinstr(arg0)), $1) != NULL/
{
      printf("%Y %5d %5d %5d %5d %-12s %-10s %25s %s\n", walltimestamp, gid, uid, pid, ppid, execname, probefunc, cwd, stringof(copyinstr(arg0)));
}