Add initial appdata file for gnome3 shop support

Screenshots are to follow.
CCMAIL:hughsient@gmail.com

krita/CMakeLists.txt

@@ -155,10 +155,12 @@ endif()
 
 install(TARGETS krita ${INSTALL_TARGETS_DEFAULT_ARGS})
 install(TARGETS kdeinit_krita ${INSTALL_TARGETS_DEFAULT_ARGS})
-install( PROGRAMS  krita.desktop  DESTINATION ${XDG_APPS_INSTALL_DIR})
-install( FILES  kritapart.desktop  DESTINATION ${SERVICES_INSTALL_DIR})
-install( FILES  krita.rc DESTINATION ${DATA_INSTALL_DIR}/krita)
+install(PROGRAMS krita.desktop  DESTINATION ${XDG_APPS_INSTALL_DIR})
+install(FILES  kritapart.desktop  DESTINATION ${SERVICES_INSTALL_DIR})
+install(FILES  krita.rc DESTINATION ${DATA_INSTALL_DIR}/krita)
+install(FILES  krita.appdata.xml DESTINATION ${SHARE_INSTALL_PREFIX}/appdata/ )
 
 add_subdirectory(tablettester)
 add_subdirectory(sketch)
 add_subdirectory(gemini)
+

krita/krita.appdata.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<application>
+  <id type="desktop">krita.desktop</id>
+  <licence>CC0</licence>
+  <description>
+    <p>Krita is the full-featured digital art studio.</p>
+
+    <p> It is perfect for sketching and painting, and presets an end–to–end solution for creating digital painting files from scratch by masters.</p>
+
+    <p>Krita is a great choice for creating concept art, comics, textures for rendering and matte paintings.</p>
+
+    <p>Have fun painting!</p>
+  </description>
+  <url type="homepage">http://www.krita.org/</url>
+  <screenshots>
+    <screenshot type="default"></screenshot>
+    <screenshot></screenshot>
+  </screenshots>
+  <updatecontact>foundation@krita.org</updatecontact>
+  <project_group>KDE</project_group>
+</application>