arian
adding disableStart option for Picker.Date.Range
The idea behind the option I propose, view code through my fork modification of file Picker.Date.Range.js, is to prevent users from inadvertently changing the start date field value. When the Picker.Date.Range object has been initialized to start at a certain date, the value is likely to change if the user clicks more than once over the Picker.Date.Range control. With the implementation of the disableStart option, and when this option is set to true, the start date input from the Picker.Date.Range control is attributed readonly, i.e. disables the user from selecting this input field, and despite the number of clicks over the Picker.Date.Range control, the start date field's value will remain the initialized value.
