[BUGFIX] Page module title obeys language overlay

Makes the page backend module's headline language overlay aware.

The displayed headline is the page title of the selected page.
But the displayed headline should also consider the selected language.

Change-Id: Ie8b3b81139b9618ac5d2331dc86be5e5cad613d5
Resolves: #39106
Releases: 6.1
[BUGFIX] Toolbar items with separator: fix white-space

The toolbar function could output erroneous html is case
additional toolbar items do not bring additionalAttributes.

Additional attributes are defined based on ToolbarItemHookInterface.
But additionalAttributes can be an empty string:

Fix output <liclass="separator"> to <li class="separator">
by adding an extra white-space.

Change-Id: I09338d17848c8fc74b25e7c532d6ee329956321b
Fixes: #45795
Releases: 6.0, 6.1
[TASK] Remove default files (DirectoryIndex)

Few default files are included in the directories typo3 and install
in case the server does not have the necessary DirectoryIndex.

Those can be removed since php is needed and DirectoryIndex
will include index.php in standard setup.

Change-Id: I5b5660b8f74242bd0924c89e105dee6dbb278fb8
Fixes: #45786
Releases: 6.1
[TASK] Remove unused files: images & templates

Most images in typo3/gfx are not used anymore.
Also several html templates are not in use any more.
Removes few image and template files.

Change-Id: Icb609e20a188e19df49aee9173f599af0f087d9a
Fixes: #45785
Releases: 6.1