Minor enhancement to attachement browser

[Kartoch]

Just an enhancement for attachement browser since it now supports drag-and-drop: It would be great if icons have the same look that Nautilus

An other minor enhancement: when creating the directory when pushing the button "create directory" in Attachement Browser, it would be interesting that:
* attachement browser window is automatically refresh (instead to refresh by pushing the dedicated button)
* no nautilus window is open (as now the attachement browser window can be used as a drag-and-drop access ti attachement directory

[Jaap Karssenberg (jaap.karssenberg)]

Please do not combine multiple requests in one report, hard for me to keep track of them that way, so I rather see 1 report per request or issue

[Jaap Karssenberg (jaap.karssenberg)]

FYI: improving widget so it will accept drag&drop even when the folder does not yet exist. This should resolve items 2 & 3.