fix jQueryUI layout's z-index issue that the resizer has higher z-index than the panels
fix jQueryUI layout's z-index issue that the resizer has higher z-index than the panels


Former-commit-id: 01ca2a5dd00bfd2bc1d09f63a2ddc2db7bd05495
webgme/webgme-engine,webgme/webgme-engine,webgme/webgme-engine