webui: add filter to attributes widget
    
    Adds filter field to attribute box in permissions for better user
    experience. User can then quickly find the desired attribute.
    
    Initial version of the patch authored by: Adam Misnyovszki
    
    https://fedorahosted.org/freeipa/ticket/4253
    
    Reviewed-By: Endi Sukma Dewata <edewata@redhat.com>