#10 grsync.desktop fixes

[Voyageur]

Downstream Gentoo bug: https://bugs.gentoo.org/742788

We have checks running at install on .desktop files, these 2 are reported on grsync one:
* /usr/share/applications/grsync.desktop: error: (will be fatal in the future): value "grsync.png" for key "Icon" in group "Desktop Entry" is an icon name with an extension, but there should be no extension as described in the Icon Theme Specification if the value is not an absolute path
* /usr/share/applications/grsync.desktop: warning: value "Application;System;" for key "Categories" in group "Desktop Entry" contains a deprecated value "Application"

Attached patch fixes both

[Piero Orsoni]

Committed to svn, many thanks!