AUI-1770 Field rendering should be separate from field editing

This is creating FormField, the class responsible for rendering fields. The form builder fields will extend from it, and add the FormBuilderFieldBase augmentation, which will enable the editing features.
AUI-1770 Refactors the rendering logic from FormBuilderFieldSentence
AUI-1770 Refactors the rendering logic from FormBuilderFieldText
AUI-1770 Adds a demo for the separate field rendering