add OC.Breadcrumb.show(dir, filename, link)

This adds a cenvenience method tho change the breadcrumbs at will, even when other controls are present.
The breadcrumbs will be prepended to the #controls, leaving any actions / buttons intact.

I needed this to fix the texteditor showing the wrong crumbs.

Test this in the console via `OC.Breadcrumb.show('/Shared/p+i&c t u r äs/df/s/gf/jj/')` or to reset to current folder `OC.Breadcrumb.show($('#dir').val())`

The two parameters `filename` and `link` are optional and will add the corresponding leaf.

This also always adds the Home icon. @owncloud/designers I assume the Home icon should always be present in the file app ... currently it is only visible in subfolders, but that's another issue.

@kabum @karlitschek @icewind1991 @jancborchardt please review