Notifications module and improved programmers API

• New: Notification module: Receive SMS-notifications when various actions occur in WordPress
  • BETA: Please get in touch if you have ideas/suggestions for improving this feature.
• New: Default country code field setting (previously all country selectors defaulted to +45/Denmark).
• New: Programmer actions gwapi_form_subscribe and gwapi_form_unsubscribe added. The first is triggered when new recipients complete signup via
  our shortcode-forms and the latter on unsubscription via the shortcode-forms.
• Optimization: Removed various unneeded dependencies.
• Danish translation updated, including the notification-module.
• Readme updated to inform about notification-module and other text improvements.