add option to clear user backends
add option to clear user backends

xx621998xx/server,pollopolea/core,pixelipo/server,michaelletzgus/nextcloud-server,owncloud/core,jbicha/server,endsguy/server,Ardinis/server,pollopolea/core,xx621998xx/server,pixelipo/server,andreas-p/nextcloud-server,lrytz/core,owncloud/core,pollopolea/core,IljaN/core,whitekiba/server,michaelletzgus/nextcloud-server,nextcloud/server,IljaN/core,whitekiba/server,andreas-p/nextcloud-server,andreas-p/nextcloud-server,pmattern/server,xx621998xx/server,owncloud/core,cernbox/core,endsguy/server,whitekiba/server,nextcloud/server,nextcloud/server,pollopolea/core,lrytz/core,sharidas/core,pmattern/server,xx621998xx/server,owncloud/core,bluelml/core,nextcloud/server,cernbox/core,Ardinis/server,endsguy/server,bluelml/core,Ardinis/server,jbicha/server,cernbox/core,IljaN/core,lrytz/core,owncloud/core,jbicha/server,pmattern/server,whitekiba/server,endsguy/server,Ardinis/server,bluelml/core,bluelml/core,sharidas/core,IljaN/core,pixelipo/server,michaelletzgus/nextcloud-server,phil-davis/core,lrytz/core,whitekiba/server,sharidas/core,pmattern/server,andreas-p/nextcloud-server,Ardinis/server,pollopolea/core,lrytz/core,endsguy/server,pixelipo/server,IljaN/core,cernbox/core,pixelipo/server,xx621998xx/server,sharidas/core,cernbox/core,sharidas/core,jbicha/server,pmattern/server,andreas-p/nextcloud-server,michaelletzgus/nextcloud-server,bluelml/core,jbicha/server