added head yield in defalt layout to support custom survey css_url feature
added head yield in defalt layout to support custom survey css_url feature

HeHStudy/surveyor,blueboard/surveyor,blueboard/surveyor,lampo/surveyor,fhisamoto/surveyor,NUBIC/surveyor,NUBIC/surveyor,alanjcfs/surveyor,bricesanchez/surveyor,Guestfolio/surveyor,lampo/surveyor,risuiowa/surveyor,risuiowa/surveyor,serracorwin/surveyor,bricesanchez/surveyor,markedmondson/surveyor,anitsirc/surveyor,alanjcfs/surveyor,bricesanchez/surveyor,bricesanchez/surveyor,Guestfolio/surveyor,lampo/surveyor,markedmondson/surveyor,alanjcfs/surveyor,NUBIC/surveyor,fhisamoto/surveyor,Guestfolio/surveyor,risuiowa/surveyor,HeHStudy/surveyor,HeHStudy/surveyor,anitsirc/surveyor,risuiowa/surveyor,blueboard/surveyor,markedmondson/surveyor,fhisamoto/surveyor,serracorwin/surveyor,fhisamoto/surveyor,Guestfolio/surveyor,anitsirc/surveyor,alanjcfs/surveyor,blueboard/surveyor,anitsirc/surveyor,lampo/surveyor,serracorwin/surveyor,HeHStudy/surveyor