[TASK] Use @TYPO3/ as ES6 module namespace

Switch from TYPO3/CMS/ExtName/ to @typo3/ext-name/ module
namespace in all TypoScript modules in order to
use the common "scoped package" syntax as known from npmjs.

This will allow TYPO3 TypeScript declarations to be
published to @TYPO3/* packages on npmjs.com at some point,
allowing extension authors to require these as npm/yarn
dependencies to be able to use TypeScript type declarations
when developing against the TYPO3 JavaScript API.

While at it, the naming convention of JavaScript modules is
also switched to use lowercase-dashed form. This is to adhere
to the common used naming convention in the npm-world.
Also @typo3/core/ajax/ajax-request.js simply looks better than
a mixed form @typo3/core/Ajax/AjaxRequest.js would be.

All existing RequireJS module identifiers are mapped
to the new naming syntax in the requirejs-to-es6 bridge:
For example a requirejs call to
  TYPO3/CMS/T3editor/Element/CodeMirrorElement
will transparently be transformed to the new sc...