Build a FeatureType builder tool into the FeatureType page

[jaycrossler]

Help the user build FeatureTypes by making it easier to configure metadata. Build into:

• [x] Show FeatureTypes visually (icon, colors, size), not just with name on /maps/feature-types page
• [ ] List how many times FeatureTypes are used?
• [ ] Have a wizard to pick color and icon
• [x] Have a way to build in additional metadata
• [x] Support adding feature-specific data fields like text boxes, drop-down lists, etc