Add documents (merges foodcoops/foodsoft#353)

plugins/documents/lib/foodsoft_documents.rb

@@ -0,0 +1,9 @@
+require 'foodsoft_documents/engine'
+
+module FoodsoftDocuments
+  # Return whether the documents are used or not.
+  # Enabled by default in {FoodsoftConfig} since it used to be part of the foodsoft core.
+  def self.enabled?
+    FoodsoftConfig[:use_documents]
+  end
+end