CMS-4501 Node Permissions - Security Tab Layout Adjustments

- moved api.ui.security to api.security
- updated combobox so clicking on row will toggle selected state
- refactored api.ui.selector.list.ListBox to inherit api.dom.UlEl
Merge pull request #1057 from enonic/cms-4501

CMS-4501 Node Permissions - Security Tab Layout Adjustments