add require field in builder
Merge branch 'master' into formbilder-validation
add required input control and update template
enforce done button click, reserve input unique name, text required tested
add required to all input templatese, checkbox tested
required added to other inputs
required added to textarea
add required to number input
add min/max to number, change control text input to number type, use input event to handle both key input and mouse clicks for number input
add step to min/max number to prevent validation problem, firefox tested
validation message tested in form viewer