various fixes for breadcrumb

* icons are shown in popup menus if available
* introduced IBreadcrumb.showInBreadcrumb() and IHierarchicalStructure.showInHierarchicalStructure() to hide empty lines
* implemented same default behavior for IBreadcrumb.getBreadcrumbIcon() as in IHierarchicaltructure.getHierarchicalStructureIcon(): Return node icon if it's not a default icon
* fixed exception about isBigCell when using breadcrumb editor
* added test language and sandbox
Merge branch 'master' of github.com:mbeddr/mbeddr.core