wip: image plugin with drag and drop for hallo

[dbu]

an image plugin with several tabs to search for images, upload images and get suggestions for related images (whatever that means in your context).

• open examples/showalways.html , edit the content, click img and then click the search tab in the dialog and click ok (with or without search term, its currently ignored by the example function. it just returns a dummy result). click on one of the images, then drag the big image below into the content.
• config parameters for search and suggestion functions that return json (i.e. ajax requests)

drag and drop itself is considered part of hallo itself, thus the update to hallo.css

this is still work in progress

• dialog closes right again if the editor is not created with showAlways: true
• responsibility for the tags in suggestions is still in the plugin instead of the external functions
• drag and drop is still wobbly, layout issues
• the tabs in the dialog are somehow handmade instead of using jquery-ui. as a result, if the first tab is not visible (as in the example) there is no content at all => use a jquery-ui tab plugin if there is a reasonable one. => http://jqueryui.com/demos/tabs/
• the search result part should be generalized, even showResults could be abstracted probably. it should be the same for search and suggestions (suggestion is missing paging right now)
• on save, the drag+drop elements should be stripped out of the content
• upload is not yet made a function as search and suggestions. it should be made injected as well. (done)
• part of the suggestions thing is in _openDialog - everything inside if widget.options.loaded is null && widget.options.suggestions should be refactored into the injected function as well.