Rename minetest-icon.svg to minetest.svg - Fixes minetest#1564

-Complies with the Linux standard freedesktop icon naming specs: http://standards.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html#guidelines
-Ensures compatibility with icon themes
-Edit minetest.desktop, CMakeLists.txt and README.md to reflect this change

CMakeLists.txt

@@ -178,7 +178,7 @@ if(UNIX AND NOT APPLE)
 	install(FILES "doc/minetest.6" "doc/minetestserver.6" DESTINATION "${MANDIR}/man6")
 	install(FILES "misc/minetest.desktop" DESTINATION "${XDG_APPS_DIR}")
 	install(FILES "misc/minetest.appdata.xml" DESTINATION "${APPDATADIR}")
-	install(FILES "misc/minetest-icon.svg" DESTINATION "${ICONDIR}/hicolor/scalable/apps")
+	install(FILES "misc/minetest.svg" DESTINATION "${ICONDIR}/hicolor/scalable/apps")
 endif()
 
 if(APPLE)

README.txt

@@ -381,7 +381,7 @@ BlockMen:
 erlehmann:
   misc/minetest-icon-24x24.png
   misc/minetest-icon.ico
-  misc/minetest-icon.svg
+  misc/minetest.svg
   textures/base/pack/logo.png
 
 License of Minetest source code

misc/minetest.desktop

@@ -9,7 +9,7 @@ Comment[ja]=マルチプレイに対応した、無限の世界のブロック
 Comment[ru]=Игра-песочница с безграничным миром, состоящим из блоков
 Comment[tr]=Tek-Çok oyuncuyla küplerden sonsuz dünyalar inşa et
 Exec=minetest
-Icon=minetest-icon
+Icon=minetest
 Terminal=false
 Type=Application
 Categories=Game;