Custom validation rule for dropdowns

[itsrachelfish]

When a dropdown question is created, there should be a custom validation rule in Laravel which ensures the options are properly formatted.

Right now, administrators are given a textarea where they are expected to format the dropdown options a specific way:

option : Description for option 1
another : Another description
third : Pick this one

If the dropdown is created without using the correct formatting, it results in catastrophic laravel template errors which prevents both users and judges from viewing applications.

Related issue: #90