Auth0 module

• auth0. Support to Auth0 as an alternative to Amazon Cognito.
• ⚠️ The ionicExtraModules array in the environments file of a project now needs to include (when needed) the variables entry (e.g. ionicExtraModules[..., 'variables']) — previously it was implicitly included. This configuration allows the automatic loading of the variables/xx.json translations dictionary file.