Provide additional information on the admin form

Problem/Motivation

Currently, the main module requires one of the widget 'sub modules' to be enabled to populate the admin form, this can be confusing to an end user.

Steps to reproduce

1. Enable the module without enabling one of the widget sub modules
2. Go to the admin page

Proposed resolution

1. Provide a message advising there are no widgets to configure and to enable one of the sub modules
2. In the form alters per widget, then ensure this message is not present if the form is populated with meaningful config options