Allow imagemap editor to point to a target within the document.

The help on imagemap says-
"If you want to jump to an anchor within the document, the address should be of
the form file:///C/document_name#anchor_name "

This means an absolute address of the target document is required. 
But if the target lies within the SAME document, then there is no need for a
relative address: Just the anchor's name should be sufficient.

Desired: Let the author specify targets within document.

Provide the "target in document" (the red bulls' eye) button in the ImageMap's
window. When this button is clicked, the target in window should pop up (and
stay open). After this, let the user define various shapes
(rectangle/ellipse/polygon) and link them with the desired bookmark/heading
within the document.

Of course, there is no need to save the arrangement as a map.