Bug#804936: cantata: fix dependencies

[HJ]

Package: cantata
Version: 1.5.2.ds2-3
Severity: normal

Dear Maintainer,

according to the github readme https://github.com/CDrummond/cantata/blob/master/README
cantata can be build without any KDE dependencies as plain qt application. So it would
be nice to have a Qt-only build like quassel and others have.

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.2.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)