Improve the access denied (403) page

This is an improved version of the current access denied (403) page based on the built-in not found (404) page.

Shows a link to the CMS backend if the user is logged in and doesn't have permissions for the backend page it's trying to access, but does have permissions for the CMS backend.

Please note that the following languages are machine translated: ja, pt-br, ru and sv.
Fixed a security vulnerability
Make word wrap fluid by default
Minor
Fixes #318
Tidy up #314
Backend and frontend controllers now return a Response object and support setting the status code
Refactor how the Form widget manages fields.
Widgets no longer need to pass configuration through "options".
Begin work on a Grid form widget
Add new form field type called "number"
Grid -> DataGrid
Widgets now no longer include their alias in getId() if it matches the default alias
Add noRecordsMessage to RelationController behavior
All DateTime fields now validated in Lists
Add a more meaningful message to MassAssignmentExceptions
Added 'camel' mode for inputpreset as per #325
Add sessionKey support to RelationController.php
Use text type instead of number type, spinners are bad
ViewMaker can now check for layouts and partials without throwing an error
Allow override of relation partials