run on_start in external form block controller (the function exists in the core Controller library so we don't need to check if it exists)
run on_start in external form block controller (the function exists in the core Controller library so we don't need to check if it exists)

Former-commit-id: 92fba18a92fb295ae6e0a6d40b02fc6b8e15dece
mlocati/concrete5,rikzuiderlicht/concrete5,concrete5/concrete5,KorvinSzanto/concrete5,concrete5/concrete5,MrKarlDilkington/concrete5,deek87/concrete5,mainio/concrete5,jaromirdalecky/concrete5,triplei/concrete5-8,haeflimi/concrete5,biplobice/concrete5,concrete5/concrete5,jaromirdalecky/concrete5,hissy/concrete5,hissy/concrete5,olsgreen/concrete5,a3020/concrete5,hissy/concrete5,MrKarlDilkington/concrete5,acliss19xx/concrete5,olsgreen/concrete5,mlocati/concrete5,deek87/concrete5,haeflimi/concrete5,mainio/concrete5,biplobice/concrete5,concrete5/concrete5,haeflimi/concrete5,mlocati/concrete5,olsgreen/concrete5,mainio/concrete5,KorvinSzanto/concrete5,acliss19xx/concrete5,rikzuiderlicht/concrete5,biplobice/concrete5,mlocati/concrete5,a3020/concrete5,triplei/concrete5-8,acliss19xx/concrete5,deek87/concrete5,jaromirdalecky/concrete5,haeflimi/concrete5,MrKarlDilkington/concrete5,triplei/concrete5-8,rikzuiderlicht/concrete5,deek87/concrete5,KorvinSzanto/concrete5,jaromirdalecky/concrete5,biplobice/concrete5,hissy/concrete5