Bug#904612: packaging of qcoan fully revised

[Elmar Stellnberger]

The packaging quality of qcoan has been highly improved since my 
original RFS. There are no more lintian errors that should be resolved 
and with the advice from wRAR at #debian-mentors I have improved the 
package internals (no nested .tar.bz2, debian/install list).

see: https://mentors.debian.net/package/qcoan