Document content element anchors

[cweiske]

Current behavior

There is no editor documentation about creating links to specific content elements.

Expected behavior/output

The editor's tutorial should talk about:

• that every content element has its own anchor ID (c + element ID)
• the link wizard can create links to single content elements
• how to create named anchors on pages (via the HTML content element)

[brotkrueml]

One addition: "that every content element has its own anchor ID" -> "that every content element provided by TYPO3 itself with a header has its own anchor ID"
... and: as long as the integrator hasn't removed that feature by overriding the templates.