Add some free icons, based on the Silk set, to draw the tree.
- [DH] itkacl-web-1.0/web/img/base-folder.png
- [DH] itkacl-web-1.0/web/img/folder-closed-moresiblings.png
- [DH] itkacl-web-1.0/web/img/folder-closed.png
- [DH] itkacl-web-1.0/web/img/folder-nochildren-moresiblings.png
- [DH] itkacl-web-1.0/web/img/folder-nochildren.png
- [DH] itkacl-web-1.0/web/img/folder-open-moresiblings.png
- [DH] itkacl-web-1.0/web/img/folder-open.png
- [DH] itkacl-web-1.0/web/img/verticalbar.png
- [DH] itkacl-web-1.0/web/img/whitespace.png