TYPO3 Core

The attached patch will add the following features to the link insertion dialogue:
1. allow to configure the class attribute as required, for all tabs or for a specific tab; the blank option is then removed from the class selector;
2. allow a hooking browser to replace the onChange attribute of the class selector;
3. allow to configure the title attribute as read only, for all tabs or for a specific tab; the title is then completely determined by the class configuration;
4. allow a hooking browser to add additional attributes on the inserted/updated a-tag; forward the additional values as dialogue query parameters;
5. allow a hooking browser to modify the body tag of the dialogue window and to add additional JS libraries.

The patch also includes some cleanup.

(issue imported from #M9775)