Merge form-field molecules #93

Similar to #90, I'm proposing we merge the various form-field molecules into a single component with the ability to specify the field type. They are all using the same class and stylesheet, as well as have lots of overlapping functionality that would benefit from consolidation.

This is related to #86 because the components in the form-fields folder in molecules need to remain together since they are using the same stylesheet. I don't want to break them up into their own folders and duplicate the styles if we are just going to be merging them anyway.