n2s_briefDisplay support for hover state objects in customSVG canvas

[roikle]

Suggestion: it would be great if customSVG canvas' could display the brief of a document which is linked to a svg element.

Justification: This would allow consistent functionality throughout the atlas framework, with both the customSVG canvas and tradition map view working in a similar fashion. It would also provide users the option of not needing to click on a svg element to see what document it's linked to, since the brief could provide summary about the document.