Theme manager

This is the first implementation of a theme manager. It’s a rebased and
revisited version of #792.

themes/CMakeLists.txt

@@ -0,0 +1,22 @@
+# CMakeLists for themes directory
+#
+# add themes subfolders
+
+SET(defthemes
+    Default
+    Fabric
+    Leather
+    Plasma
+    VelvetMarble
+)
+
+if(UNIX)
+    if(APPLE)
+        INSTALL(DIRECTORY ${defthemes} DESTINATION cockatrice.app/Contents/Resources/themes/)
+    else()
+        # Assume linux
+        INSTALL(DIRECTORY ${defthemes} DESTINATION share/cockatrice/themes/)
+    endif()
+elseif(WIN32)
+    INSTALL(DIRECTORY ${defthemes} DESTINATION themes/)
+endif()