Optimize the package in size

Get rid of the 'convert' and it's libraries since it's already included
in the NAS OS.

Move the common twonkyserver/cgi-bin/*.{desc,location} files to its
own directory

Add check if Twonky Server executable does exist in the twonkyserver-${arch}
folder

Switch let it run as admin user/group
Modfiations for running service as admin
Fix typos, use official log and correct abs. path
Update README.md with a modest how-to