Adding notification class.
Adding a notifications table.
Adding notification table output.
Adding functions for interacting with notifications.
Adding table for notifications.
Added table layout for notifications settings
Added notification activation code.
Merge branch 'feature/notifications' of https://github.com/wpninjas/ninja-forms into feature/notifications

Conflicts:
	classes/notifications.php
Fixing merge conflicts.
Continuing to work on the notification table.
Continuing to work on the notification table.
Adding a registration class for fields, notifications, and sidebars.
Creating a notification types class to instantiate all of our registered notification types.
Adding specific notification types.
Creating some initial notification types.
Merge branch 'develop' into feature/notifications

Conflicts:
	includes/deprecated.php
	ninja-forms.php
Merge branch 'develop' into feature/notifications
Merging develop into notifications.
Adding notification-related functions.
Adding notifications.