Improving fonts spec

[Luya Tshimbalanga]

The current packaged template for fontpackages are out of date for the
following reasons.

- Use of obsolete "rm -fr %{buildroot} in %install inside fontpackages
(https://bugzilla.redhat.com/show_bug.cgi?id=1271620)

- Inclusion of appdata for fonts allowing ease of detection for Gnome
Software or any appstream related applications. You can view an example on
http://pkgs.fedoraproject.org/cgit/rpms/julietaula-montserrat-fonts.git/tree...
http://pkgs.fedoraproject.org/cgit/rpms/gpick.git/tree/gpick.spec

Here is a guideline for appdata on
https://fedoraproject.org/wiki/Packaging:AppData