Removed obsolete build dependency libqt4-dev (Closes: #875026)

* Switched to debhelper-compat (=12)
* Removed not needed build dependency d-shlibs
* Bumped Standards-Version to 4.4.0, no changes needed
* Removed Qt4 packages from control and fixed the description of Qt5 packages
* Modified debian/rules to fit Qt5 only builds
* Don't provide statically linked files anymore
* Added the now needed install files
* Fixed symbols for gcc-9
* Added Build-Depends-Package field to symbols
* Removed superfluous Section entry from libquazip5-1
* Removed obsolete libquazip5-headers package, combined with -dev,
  -dev is useless without -headers and vice versa - and it doesn't hurt
  if a cmake file is installed in non-cmake builds. Set Breaks and Replaces.
* Added myself to copyright
* Added myself to uploaders