Add new access role to ThumbnailIconController

[abdeje]

We have an issue with the roles set on the controller, because some of our editors has limited access and none of the goups applied to day.

It would be nice to have an extra group like ThumbnailGroup, that you can use to set access rights with.
[Authorize(Roles = "Administrators, CmsAdmins, CmsEditors, WebAdmins, WebEditors, ThumbnailGroup")]

[degborta]

@abdeje Sorry for the late reply! I'll take a look and do something to handle this.

[degborta]

@abdeje Version 1.2.0 is uploaded to Episerver Nuget feed and should be available soon.