Add `count` to Themes and ColorSchemes

lib/gitlab/color_schemes.rb

@@ -32,6 +32,11 @@ module Gitlab
       SCHEMES.detect { |s| s.id == id } || default
     end
+    # Returns the number of defined Schemes
+    def self.count
+      SCHEMES.size
+    end
+
     # Get the default Scheme
     #
     # Returns a Scheme

lib/gitlab/themes.rb

@@ -37,6 +37,11 @@ module Gitlab
       THEMES.detect { |t| t.id == id } || default
     end
+    # Returns the number of defined Themes
+    def self.count
+      THEMES.size
+    end
+
     # Get the default Theme
     #
     # Returns a Theme