Improve RPM Spec file

Clean up redundant code, use currently recommended macros and file properties.

Diff example:

 %prep
-%setup -q -n %{name}-%{version}
-
-# >> setup
-# << setup
+%autosetup
 
 %build
-# >> build pre
-# << build pre
-
 %qmake5
 %make_build
 
-# >> build post
-# << build post
-
 %install
-rm -rf %{buildroot}
-%qmake5_install
-
-desktop-file-install --delete-original  \
---dir %{buildroot}%{_datadir}/applications \
-%{buildroot}%{_datadir}/applications/*.desktop
+%make_install
 
 %files
 %defattr(-,root,root,-)
-%{_bindir}
+%{_bindir}/%{name}
 %defattr(644,root,root,-)
 %{_datadir}/%{name}
 %{_datadir}/applications/%{name}.desktop
 %{_datadir}/icons/hicolor/*/apps/%{name}.png
-# >> files
-# << files