Add configurable about this dataset links (#907)

* add about arg

* add simple url validator

* attach about link to config api

* add links to configDefaults

* add conditional link in top left and menu item

* whitespace

* change to lower case

* move --about arg before click.command()

if this fixes it I have no idea why

* change link>URL

* be more descriptive about URL

* Make error more explicit

* refactor attach_data to accept about

* format

* change icon

* add trailing parenthesis

* whitespace

server/app/app.py

@@ -33,6 +33,6 @@ class Server:
         self.app.register_blueprint(resources.blueprint)
         self.app.add_url_rule("/", endpoint="index")
 
-    def attach_data(self, data, title="Demo"):
-        self.app.config.update(DATASET_TITLE=title)
+    def attach_data(self, data, title="Demo", about=""):
+        self.app.config.update(DATASET_TITLE=title, ABOUT_DATASET=about)
         self.app.data = data