Misc. Bugfixes and improvements.

- Added Support for FitMode.Pad in thumbnail generation.
- Added CodeMirror for editing json-content.
- Added Support for fileGroups in draft templates.
- Added CONTAINER as Stock-Node-Type.
- Changed default FitMode- and ScaleMode-Values for thumbnails shown in
the cms-ui.
- Invalidate Cache after deleting Thumbnails.
- Include file metadata in sitemap. (WebsiteController)
Added UI for insertLinkDialog. Expand Tree-Nodes...

... on selection.
- Show template description in template gallery.
- Misc visual changes.
Fixed upload progress display.

- Always ensure that filegroups defined in the template exist in draft
editor.
- Enabled "copy original" in translation editor.
- Show thumbnails in draft and publication detail view.
- Reviewed css. Started clean up.
Use CodeMirror for HTML-Content.
Reorded bottom navbar content. Fixed Issues...

...found by jshint. Reviewed publishDraftView.
Added DbSiteMapNodeResource.PictureFileVersion.