Editing a Chart

1. The user opens an XWiki page containing coresponding to a particular chart either by following a link (e.g. clicking on the embeded chart) or entering the right URL.
2. The user selects the "Edit Chart" option in the "More Actions" menu.
3. An XWiki page containing a wizard similar to the one for creating charts is displayed (see XWIKI-137). The difference is that all wizard steps are enabled.
4. The user modifies as many options as he wants.
5. After the user clicks "Finish", the chart definition is updated, and the page containing the updated chart is redisplayed.