feat datepicker: Adding a variable to specify the date format used by controller
feat datepicker: Adding a variable to specify the date format used by controller

The datepicker controller was using a constant value for date format ('LL').
And sometimes, we could show our date in dd/MM/yyyy format instead of
text. So now, we can specify the date formate used by moment ('L','LL',etc)
in the directive.

daniel-oliveiravas/lumX,daniel-oliveiravas/lumX,daniel-oliveiravas/lumX,daniel-oliveiravas/lumX